MDCAT 2022 Physics

MDCAT 2022 Physics Past Paper MCQs with Answers

281 Physics MCQs that appeared in MDCAT 2022, arranged unit by unit in syllabus order. Tap “Show answer” under any question for the correct option and a short solution.

Vectors and Equilibrium

1.Force is a: (PMC MDCAT 2022)

  1. Vector
  2. Scalar
  3. Tensor
  4. Base quantity
Show answer

Correct answer: (a) Vector

Force has both magnitude and direction and adds by the parallelogram rule, so it is a vector.

Force and Motion

2.Which of the following is the correct definition of variable velocity? (MDCAT 2022)

  1. unequal distances are covered in equal intervals of time
  2. equal displacements are made in unequal intervals of time
  3. unequal displacements are made in equal intervals of time
  4. equal displacements are made in equal intervals of time
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Correct answer: (c) unequal displacements are made in equal intervals of time

Velocity is displacement per unit time, so it varies when the displacement in equal times is unequal.

3.Q.77 The time rate of change of velocity is called: (NUMS MDCAT 2022)

  1. Force
  2. Acceleration
  3. Power
  4. Energy
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Correct answer: (b) Acceleration

The rate of change of velocity is the acceleration.

4.Two buses moving at 100 km/h and 80 km/h respectively cross each other while moving in opposite direction. Velocity of one bus relative to other bus is: (NUMS MDCAT 2022)

  1. 100 km/h
  2. 20 km/h
  3. 80 km/h
  4. 180 km/h
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Correct answer: (d) 180 km/h

Moving towards each other, the speeds add: $100+80$ is $180\,\mathrm{km\,h^{-1}}$.

5.A stone thrown horizontally from the top of a tall building follows a path that is: (MDCAT 2022)

  1. circular
  2. made of two straight line segments
  3. hyperbolic
  4. parabolic
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Correct answer: (d) parabolic

The horizontal velocity is constant and the vertical motion is uniformly accelerated, and the two together give a parabola.

6.In a projectile motion, velocity at maximum height is: (PMC MDCAT 2022)

  1. usinθ
  2. ucosθ
  3. utanθ
  4. ucotθ
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Correct answer: (b) ucosθ

The vertical component is spent at the top, leaving the horizontal component $u\cos\theta$.

7.In the absence of air resistance, an object thrown into the air at an angle of 20 degrees to the ground. It will experience: (PMC MDCAT 2022)

  1. Constant vertical acceleration
  2. Changing vertical acceleration
  3. Changing horizontal acceleration
  4. Constant (non zero) horizontal acceleration
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Correct answer: (a) Constant vertical acceleration

Gravity is the only force, so the vertical acceleration is $g$ throughout and the horizontal one is nil.

8.Which of the following quantities has no effect on simple projectile motion? (PMC MDCAT 2022)

  1. Velocity
  2. Force
  3. Mass
  4. Acceleration
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Correct answer: (c) Mass

The path depends on the launch velocity and on $g$ alone, so the mass makes no difference.

9.The horizontal range is 4√3 times of the maximum height. Its angle of projection is: (PMC MDCAT 2022)

  1. 90 degrees
  2. 45 degrees
  3. 60 degrees
  4. 30 degrees
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Correct answer: (d) 30 degrees

$R=4\sqrt3H$ gives $\tan\theta=4/(4\sqrt3)$, so $\theta$ is $30^{\circ}$.

10.At what angle of projectile horizontal range is minimum: (PMC MDCAT 2022)

  1. 30 degrees
  2. 45 degrees
  3. 60 degrees
  4. 90 degrees
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Correct answer: (d) 90 degrees

$\sin2\theta$ is zero at $90^{\circ}$, so the projectile goes straight up and comes straight down.

11.For a projectile at angle (45+θ) and (45-θ), the ratio of horizontal range described by the projectile is: (PMC MDCAT 2022)

  1. 1.00
  2. 0.50
  3. 2.00
  4. 0.08
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Correct answer: (a) 1.00

The two angles add to $90^{\circ}$, so their ranges are equal and the ratio is one.

12.The projectile motion covers maximum range: (PMC MDCAT 2022)

  1. Horizontally
  2. Vertically
  3. Tangentially
  4. Linearly
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Correct answer: (a) Horizontally

The range of a projectile is measured along the horizontal.

13.If a particle launched with 5m/s at angle of 45 degree, then time of flight is: (PMC MDCAT 2022)

  1. 1.44 s
  2. 0.72 s
  3. 0.6 s
  4. 0.5 s
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Correct answer: (b) 0.72 s

$T=2u\sin\theta/g=2\times5\times0.707/9.8$, about $0.72\,\mathrm{s}$.

14.Q.78 In projectile motion, the rage of projectile will be maximum at an angle of: (NUMS MDCAT 2022)

  1. 30 degrees
  2. 45 degrees
  3. 60 degrees
  4. 90 degrees
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Correct answer: (b) 45 degrees

The range goes as $\sin2\theta$, which is largest at $45^{\circ}$.

15.Which of the following pair of angles have same rang for a projectile? (NUMS MDCAT 2022)

  1. 10° and 20°
  2. 75° and 15°
  3. 45° and 60°
  4. 0° and 30°
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Correct answer: (b) 75° and 15°

Two angles adding to $90^{\circ}$ give the same range.

16.A fireman slides down a rope whose breaking load is three quarters of his weight. With what acceleration should the fireman slide down, if the acceleration due to gravity is $g$? (MDCAT 2022)

  1. $g$
  2. $g/4$
  3. $3g/4$
  4. zero
Show answer

Correct answer: (b) $g/4$

The rope can pull up with at most $\tfrac{3}{4}mg$, so $ma=mg-\tfrac{3}{4}mg$ and $a=g/4$.

17.Is it possible to have a non-zero number of forces acting on an object (of non-zero mass), yet the object doesn’t accelerate? (PMC MDCAT 2022)

  1. No
  2. Yes
  3. Not necessarily
  4. Not enough information
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Correct answer: (b) Yes

If the forces balance, the resultant is zero and the body does not accelerate.

18.Which of the following is true about newton’s laws of motion? (PMC MDCAT 2022)

  1. One of them is not related to forces
  2. Two of them are not related to forces
  3. All of them are related to forces
  4. One of them is related forces
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Correct answer: (c) All of them are related to forces

The first defines force, the second measures it and the third pairs it with its reaction.

19.The value of acceleration due to gravity: (PMC MDCAT 2022)

  1. Is same on equator and poles
  2. Is least on poles
  3. Is least on equator
  4. Increases from pole to equator
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Correct answer: (c) Is least on equator

The Earth bulges at the equator, so the surface there is furthest from the centre and $g$ is least.

20.An eagle of mass 4 kg is locked inside a cage of mass 2 kg. If the eagle starts flying, what will be the mass of the bird and cage assembly? (PMC MDCAT 2022)

  1. 5 kg
  2. 7 kg
  3. 2 kg
  4. 6 kg
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Correct answer: (d) 6 kg

The cage is closed, so the eagle and the cage remain one system of $6\,\mathrm{kg}$ whether it flies or not.

21.A man of mass 50 kg on the top floor of a skyscraper steps into an elevator. (PMC MDCAT 2022)

  1. 460 N
  2. 325 N
  3. 425 N
  4. 475 N
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Correct answer: (c) 425 N

With the lift accelerating down, the floor pushes up with $m(g-a)=50\times8.5$, that is $425\,\mathrm{N}$.

22.A car and truck is running with same velocity, a constant and same force applied to both, which will stop first: (PMC MDCAT 2022)

  1. Car
  2. Truck
  3. Both at the same time
  4. Information insufficient
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Correct answer: (a) Car

The same force acting for the same change of velocity stops the smaller mass first.

23.A gun fires a bullet of mass 40 g with a velocity of 1200 ms-1 . The man holding it can exert a maximum force of 144 N on the gun. How many bullets can he fire per second at the most? (PMC MDCAT 2022)

  1. 1
  2. 2
  3. 3
  4. 4
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Correct answer: (c) 3

Each shot carries $0.04\times1200=48\,\mathrm{N\,s}$ of momentum, and $144/48$ is three a second.

24.A force of 50 dynes is acted on a body of mass 5g which is at rest for an interval of 3 seconds, then impulse is (PMC MDCAT 2022)

  1. 0.00015 N.s
  2. 0.0015 N.s
  3. 0.15 N.s
  4. 1.6 N.s
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Correct answer: (b) 0.0015 N.s

$50\,\mathrm{dyne}$ is $5\times10^{-4}\,\mathrm{N}$, and over three seconds the impulse is $1.5\times10^{-3}\,\mathrm{N\,s}$.

25.Which of the following is incorrect? (MDCAT 2022)

  1. the reaction force on a body is always balanced by the action force on the same body
  2. reaction and action forces are always equal in magnitude
  3. action and reaction forces never act on the same body
  4. Newton's third law is always valid
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Correct answer: (a) the reaction force on a body is always balanced by the action force on the same body

Action and reaction act on two different bodies, so they can never balance each other on one body.

26.Two bodies in contact experience forces in: (PMC MDCAT 2022)

  1. Same direction
  2. Opposite directions
  3. Perpendicular directions
  4. five different direction
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Correct answer: (b) Opposite directions

Action and reaction are equal and opposite.

27.Conservation of momentum is always applicable in a: (PMC MDCAT 2022)

  1. Open system
  2. Closed system
  3. Isolated system
  4. Any system
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Correct answer: (c) Isolated system

Momentum is conserved when no external force acts, that is in an isolated system.

28.While moving a boat forward we have to: (PMC MDCAT 2022)

  1. Push water forward
  2. Push water backward
  3. Keeps the water steady
  4. Keeps the water undisturbed
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Correct answer: (b) Push water backward

The oar pushes the water back and the water pushes the boat forward.

29.The horse pulling the wagon is able to move forward because of: (PMC MDCAT 2022)

  1. The force exerted by the horse on the ground
  2. The force exerted by the ground on the horse
  3. The force exerted by the wagon on the horse
  4. The force exerted by the horse on the wagon
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Correct answer: (b) The force exerted by the ground on the horse

The horse pushes back on the ground and the ground pushes it forward.

30.If a bird catches its prey from a height which was initially at rest then momentum will be conserved for: (PMC MDCAT 2022)

  1. Bird
  2. Prey
  3. Either bird and prey
  4. Both bird and prey
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Correct answer: (d) Both bird and prey

No outside force acts on the pair, so the momentum of the bird and prey together is conserved.

31.The total momentum of a flock of identical birds could be zero only if the birds are: (PMC MDCAT 2022)

  1. Taking off from the ground
  2. Flying in the same direction
  3. Flying in different dlrections
  4. Very tired and coming down to rest
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Correct answer: (c) Flying in different dlrections

Momentum is a vector, so equal and opposite momenta can cancel only if the birds fly different ways.

32.Q.79 Which of the following is NOT TRUE? (NUMS MDCAT 2022)

  1. Action and reaction have same nature
  2. Action and reaction have same line of action
  3. Action and reaction never act on same body
  4. Action and reaction can cancel each other
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Correct answer: (d) Action and reaction can cancel each other

They act on different bodies, so they can never cancel one another.

33.A wagon weighing 1000kg is moving with a velocity 50 km/h on smooth horizontal rails. A mass of 250kg is dropped into it. The velocity with which it moves in km/h now is: (PMC MDCAT 2022)

  1. 20 km/h
  2. 60 km/h
  3. 40 km/h
  4. 25 km/h
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Correct answer: (c) 40 km/h

$1000\times50=1250v$, so $v$ is $40\,\mathrm{km\,h^{-1}}$.

34.Q.76 An elastic collision is the one in which: (NUMS MDCAT 2022)

  1. Kinetic energy and momentum is conserved
  2. Kinetic energy is conserved but total energy is not con-served
  3. Momentum is conserved but kinetic energy is not con-served
  4. Both kinetic energy and momentum are not conserved
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Correct answer: (a) Kinetic energy and momentum is conserved

In a perfectly elastic collision both the momentum and the kinetic energy are conserved.

35.The explosion of explosive material is application of: (NUMS MDCAT 2022)

  1. Law of conservation of energy
  2. Law of conservation of mass
  3. Law of conservation of momentum
  4. Newton's third law of motion
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Correct answer: (c) Law of conservation of momentum

The fragments fly apart with momenta that add to the zero the charge began with.

Work and Energy

36.Work done by the spring force in a time interval cannot be: (PMC MDCAT 2022)

  1. Positive
  2. Negative
  3. Zero
  4. Constant
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Correct answer: (c) Zero

The spring force and the displacement are along the same line, so their product is never zero while the spring moves.

37.A body is undergoing non uniform circular motion, work done by radial force on the body: (PMC MDCAT 2022)

  1. Positive
  2. Zero
  3. Negative
  4. Variable
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Correct answer: (b) Zero

The radial force is always at right angles to the motion, so it does no work.

38.A particle of mass $m$ at rest is acted upon by a force $P$ for a time $t$. Its kinetic energy after time $t$ is: (MDCAT 2022)

  1. $P^2t^2/m$
  2. $P^2t^2/2m$
  3. $P^2t^2/3m$
  4. $P^2t^2/4m$
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Correct answer: (b) $P^2t^2/2m$

The impulse gives $p=Pt$, and $E_k=p^2/2m=P^2t^2/2m$.

39.A ball is projected with kinetic energy E at 45 degree angle. At the highest point its kinetic energy is: (PMC MDCAT 2022)

  1. 2E
  2. 0
  3. E
  4. E/2
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Correct answer: (d) E/2

Only the horizontal component is left at the top, and at $45^{\circ}$ that carries half the energy.

40.The K.E. of object at rest Is: (PMC MDCAT 2022)

  1. Maximum
  2. Negative
  3. Zero
  4. Constant
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Correct answer: (c) Zero

$K=\tfrac12mv^2$, and at rest the speed is zero.

41.Minimum value of kinetic energy is: (PMC MDCAT 2022)

  1. Infinite
  2. Zero
  3. Negative constant
  4. Minus infinite
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Correct answer: (b) Zero

Kinetic energy is $\tfrac12mv^2$ and can never fall below zero.

42.If the kinetic energy is increased 4 times then momentum will increase: (PMC MDCAT 2022)

  1. 3 times
  2. 4 times
  3. 5 times
  4. 2 times
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Correct answer: (d) 2 times

$p=\sqrt{2mK}$, so four times the kinetic energy doubles the momentum.

43.A car and a train both have same kinetic energy. Which one has greater momentum? (PMC MDCAT 2022)

  1. Car
  2. Train
  3. Both have same
  4. No change
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Correct answer: (b) Train

$p=\sqrt{2mK}$, so at the same kinetic energy the heavier body carries the greater momentum.

44.A long spring, when stretched by a distance $x$, has potential energy $V$. On increasing the stretching to $nx$, the potential energy of the spring will be: (MDCAT 2022)

  1. $nV$
  2. $V/n$
  3. $n^2V$
  4. $V/n^2$
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Correct answer: (c) $n^2V$

$E=\tfrac{1}{2}kx^2$ goes as the square of the extension.

45.Ignoring friction and the extra forces exerted by the muscles, a pole vault is the conversion of an athlete's running kinetic energy into gravitational potential energy. If an athlete is to lift his body 5 m during a vault, what speed must he have when he plants his pole? (MDCAT 2022)

  1. $5\ \mathrm{m\,s^{-1}}$
  2. $10\ \mathrm{m\,s^{-1}}$
  3. $15\ \mathrm{m\,s^{-1}}$
  4. $20\ \mathrm{m\,s^{-1}}$
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Correct answer: (b) $10\ \mathrm{m\,s^{-1}}$

$\tfrac{1}{2}mv^2=mgh$ gives $v=\sqrt{2gh}=\sqrt{2(10)(5)}=10\ \mathrm{m\,s^{-1}}$.

46.According to mechanical energy conservation: (PMC MDCAT 2022)

  1. KE remains constant
  2. PE remains constant
  3. KE+ PE = constant
  4. Gravitatlonal energy is constant
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Correct answer: (c) KE+ PE = constant

With no friction the sum of kinetic and potential energy stays the same.

47.If the water falls from a dam on the turbine wheel 19.6 m below, then the velocity of water at the turbine is: (PMC MDCAT 2022)

  1. 9.8 m/s
  2. 19.6 m/s
  3. 32.8 m/s
  4. 98.0 m/s
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Correct answer: (b) 19.6 m/s

$v=\sqrt{2gh}=\sqrt{2\times9.8\times19.6}$, which is $19.6\,\mathrm{m\,s^{-1}}$.

48.The formula to estimate P.E is: (PMC MDCAT 2022)

  1. F.d
  2. mgh
  3. kx
  4. mvr
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Correct answer: (b) mgh

The potential energy gained in rising a height $h$ is $mgh$.

49.The amount of work done in moving a body at certain point in a gravitational field to a position of zero potential such that the body is never accelerated is called: (NUMS MDCAT 2022)

  1. Kinetic energy
  2. Potential energy
  3. Gravitational potential energy
  4. Absolute potential energy
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Correct answer: (c) Gravitational potential energy

That work is the absolute gravitational potential energy of the body at the point.

50.The consumption of energy by a 60 W bulb in 2 s is: (MDCAT 2022)

  1. 120 J
  2. 60 J
  3. 30 J
  4. 0.02 J
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Correct answer: (a) 120 J

$E=Pt=60\times2=120$ J.

51.A car is moving at a velocity of 50 m/s and then the driver puts the brake and the car comes to rest. The force applied by car in the opposite direction is 2 N. (PMC MDCAT 2022)

  1. -100 watt
  2. 0 watt
  3. 25 watt
  4. 100 watt
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Correct answer: (d) 100 watt

$P=Fv=2\times50$, which is $100\,\mathrm{W}$.

52.A block moves in uniform circular motion because a cord tied to the block is anchored at the center of the circle. What will be the power exerted on the block by the cord? (PMC MDCAT 2022)

  1. Positive
  2. Zero
  3. Negative
  4. variable
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Correct answer: (b) Zero

The cord pulls at right angles to the motion, so it does no work and delivers no power.

53.A block of mass 2 kg is moving with the velocity 5 m/s in the horizontal direction under an influence of force 20 N. How much power is delivered by normal force? (PMC MDCAT 2022)

  1. -100 W
  2. 100 W
  3. 0 W
  4. 200 W
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Correct answer: (c) 0 W

The normal force is at right angles to the motion, so it does no work and delivers no power.

54.1 kilowatt =____________ Watts. (PMC MDCAT 2022)

  1. 2000 watts
  2. 1000 watts
  3. 300 watts
  4. 100 Watts
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Correct answer: (b) 1000 watts

A kilowatt is a thousand watts.

55.A 1kW motor pumps out water from a well 10 meter deep. What is the quantity of water pumped out per second? (PMC MDCAT 2022)

  1. 9.2 kg
  2. 9.5 kg
  3. 10.2 kg
  4. 10.8 kg
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Correct answer: (c) 10.2 kg

$m=Pt/gh=1000/(9.8\times10)$, about $10.2\,\mathrm{kg}$ each second.

56.1hp is equal to: (NUMS MDCAT 2022)

  1. 476 watts
  2. 647 watts
  3. 746 watts
  4. 487 watts
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Correct answer: (c) 746 watts

One horsepower is $746\,\mathrm{W}$.

57.The product of force and velocity is equal to: (NUMS MDCAT 2022)

  1. Kinetic energy
  2. Potential energy
  3. Power
  4. Work done
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Correct answer: (c) Power

Force times velocity is power.

58.An engine pumps 400 kg of water through a height of 10 m in 40 s. Find the power of the engine if its efficiency is 80%? Take g = 10msJ\-2. (PMC MDCAT 2022)

  1. 1.25 W
  2. 125 W
  3. 1.25 kW
  4. 12.5 kW
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Correct answer: (c) 1.25 kW

The useful power is $400\times10\times10/40=1000\,\mathrm{W}$, and at $80\%$ efficiency the engine must supply $1.25\,\mathrm{kW}$.

Rotational and Circular Motion

59.The number of revolutions in $3\pi$ radians is: (MDCAT 2022)

  1. $1/60$
  2. $3/2$
  3. 3
  4. 6
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Correct answer: (b) $3/2$

One revolution is $2\pi$ radians, so $3\pi/2\pi=1.5$ revolutions.

60.Angular displacement becomes linear for ____ arc lengths: (PMC MDCAT 2022)

  1. Short
  2. Circular
  3. Curved
  4. Large
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Correct answer: (a) Short

Only for a small arc does the angular displacement behave as a vector along the axis.

61.The direction associated with angular displacement is given by : (PMC MDCAT 2022)

  1. Left-hand rule
  2. Head to tail rule
  3. Right-hand rule
  4. Fleming's rule
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Correct answer: (c) Right-hand rule

Curl the fingers of the right hand along the rotation and the thumb gives the direction.

62.Earth’s rotation in 24 hours covers ___ angle: (PMC MDCAT 2022)

  1. 90
  2. 60
  3. 57.3
  4. 360
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Correct answer: (d) 360

A full rotation is $360^{\circ}$.

63.One complete revolution of an object covers _____ angle in degrees (PMC MDCAT 2022)

  1. 180
  2. 90
  3. 360
  4. 270
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Correct answer: (c) 360

A full revolution is $360^{\circ}$.

64.During multiple revolutions, the centre of rotation is ____ (PMC MDCAT 2022)

  1. Fixed
  2. Not fixed
  3. May depend on condition of rotation
  4. There is no centre in angular motion
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Correct answer: (a) Fixed

A body in circular motion turns about an axis that stays where it is.

65.The quantity used in angular measurement is: (PMC MDCAT 2022)

  1. Perimeter
  2. Area
  3. Circumference
  4. Volume
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Correct answer: (c) Circumference

The angle in radians is the arc divided by the radius, and the whole circumference gives $2\pi$.

66.Radian can be used to measure: (PMC MDCAT 2022)

  1. length of line
  2. Diameter of circle
  3. side of traingle
  4. arc length
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Correct answer: (d) arc length

The angle in radians is the arc divided by the radius, so it measures arc length.

67.1 radian = (NUMS MDCAT 2022)

  1. 5.7°
  2. 73.5°
  3. 57.3°
  4. 37.5°
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Correct answer: (c) 57.3°

One radian is $180/\pi$ degrees, about $57.3^{\circ}$.

68.If a wheel turns at $3.0\ \mathrm{rad\,s^{-1}}$, the time it takes to complete one revolution is about: (MDCAT 2022)

  1. 0.67 s
  2. 10 s
  3. 1.3 s
  4. 2.1 s
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Correct answer: (d) 2.1 s

$T=2\pi/\omega=6.28/3.0\approx2.1$ s.

69.An object travelling in a circle at 2 revolutions per second has an angular velocity of: (PMC MDCAT 2022)

  1. 12.9 rad/s
  2. 13.3 rad/s
  3. 12.6 rad/s
  4. 14.6 rad/s
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Correct answer: (c) 12.6 rad/s

$\omega=2\pi f=2\times2\pi$, about $12.6\,\mathrm{rad\,s^{-1}}$.

70.The rotation of the earth in 1 day covers approximately ____ radian angular distance. (PMC MDCAT 2022)

  1. 6.3
  2. 7.3
  3. 10.3
  4. 5.3
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Correct answer: (a) 6.3

A full turn is $2\pi$, about $6.3$ radians.

71.When body moves in a circle _______ always changes: (PMC MDCAT 2022)

  1. Velocity
  2. Acceleration
  3. Mass
  4. Force
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Correct answer: (a) Velocity

The direction changes at every point, so the velocity is never constant.

72.Earth covers its one revolution around the Sun in: (PMC MDCAT 2022)

  1. 24 hours
  2. 7 days
  3. 12 months
  4. 60 minutes
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Correct answer: (c) 12 months

The Earth takes a year, that is twelve months, to go once round the Sun.

73.The earth rotates 360o about its axis in about 24 hours. By how many degrees will it rotate In 2 hours? (PMC MDCAT 2022)

  1. 90
  2. 60
  3. 30
  4. 15
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Correct answer: (c) 30

$360^{\circ}$ in $24$ hours is $15^{\circ}$ an hour, so $30^{\circ}$ in two.

74.A rotating wheel coincides 12 rev in 4s. find the average angular velocity in rad/sec: (NUMS MDCAT 2022)

  1. 24.6 rad/s
  2. 16.8 rad/s
  3. 10.4 rad/s
  4. 18.8 rad/s
Show answer

Correct answer: (d) 18.8 rad/s

$12\times2\pi/4$ is about $18.8\,\mathrm{rad\,s^{-1}}$.

75.A fighter plane is moving in a vertical circle of radius $r$. Its minimum velocity at the highest point of the circle will be: (MDCAT 2022)

  1. $\sqrt{3gr}$
  2. $\sqrt{2gr}$
  3. $\sqrt{gr}$
  4. $\sqrt{gr/2}$
Show answer

Correct answer: (c) $\sqrt{gr}$

At the least speed the weight alone supplies the centripetal force, so $mg=mv^2/r$ and $v=\sqrt{gr}$.

76.Centripetal force is provided by ______ in a frictional road around a circular path (PMC MDCAT 2022)

  1. Frictional force
  2. normal force
  3. gravitational force
  4. pseudo force
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Correct answer: (a) Frictional force

On a level road it is the friction of the tyres that turns the car.

77.The acceleration produced by the centripetal force is always: (PMC MDCAT 2022)

  1. Directed parallel to the center of the circle
  2. Directed perpendicular to the center of the circle
  3. Directed towards the center of the circle
  4. Directed away from the center of the circle
Show answer

Correct answer: (c) Directed towards the center of the circle

Centripetal acceleration points along the radius, towards the centre.

78.When an object experience circular motion, the direction of centripetal acceleration is: (NUMS MDCAT 2022)

  1. Towards center
  2. Along tangent
  3. Along the direction of motion
  4. Opposite of the direction of motion
Show answer

Correct answer: (a) Towards center

Centripetal acceleration points along the radius towards the centre.

Fluid Dynamics

79.When a heavy coin falls a short distance towards the ground it does not reach terminal velocity. Why is this so? (MDCAT 2022)

  1. the coin has not hit the ground
  2. the weight of the coin is equal to the air resistance
  3. the weight of the coin increases as the air resistance increases
  4. the weight of the coin is more than the air resistance
Show answer

Correct answer: (d) the weight of the coin is more than the air resistance

Terminal velocity is reached only when the drag has grown equal to the weight, and over a short fall it has not.

Waves

80.Mechanical waves are not produced in: (MDCAT 2022)

  1. electric and magnetic fields
  2. springs
  3. ropes
  4. water
Show answer

Correct answer: (a) electric and magnetic fields

A mechanical wave needs a material medium; a disturbance of the electric and magnetic fields travels without one.

81.Water waves are examples of: (PMC MDCAT 2022)

  1. Transverse waves
  2. Progressive waves
  3. Longitudinal waves
  4. Compressional waves
Show answer

Correct answer: (b) Progressive waves

A progressive wave carries energy forward through the medium.

82.___ waves always need medium to travel? (PMC MDCAT 2022)

  1. Light
  2. Stationary
  3. Sound
  4. Both sound and stationary
Show answer

Correct answer: (d) Both sound and stationary

Sound is mechanical, and a stationary wave is made of two mechanical waves, so both need a medium.

83.The velocity of sound in vacuum at 0 C: (PMC MDCAT 2022)

  1. 332 m/s
  2. 344 m/s
  3. 330 m/s
  4. 0
Show answer

Correct answer: (d) 0

Sound needs a medium, so it does not travel through a vacuum at all.

84.The shortest distance between any two points in phase on a wave is called the: (MDCAT 2022)

  1. displacement
  2. amplitude
  3. wavelength
  4. frequency
Show answer

Correct answer: (c) wavelength

That distance is one wavelength.

85.Which of the following increases by increasing the amplitude? (MDCAT 2022)

  1. wavelength
  2. frequency
  3. time period
  4. loudness
Show answer

Correct answer: (d) loudness

The energy of a wave goes as the square of the amplitude, and for sound that is heard as loudness.

86.Pitch is ___ proportional to frequency. (PMC MDCAT 2022)

  1. Directly
  2. Inversely
  3. Exponentially
  4. No effect
Show answer

Correct answer: (a) Directly

The higher the frequency the higher the pitch.

87.The property of musical sound which differentiate between grave and shrill sound is called? (PMC MDCAT 2022)

  1. Pitch
  2. Intensity
  3. Beats
  4. Quality
Show answer

Correct answer: (a) Pitch

A grave note is low and a shrill one high, so the difference is one of pitch.

88.Pitch depends upon: (PMC MDCAT 2022)

  1. Frequency
  2. Timbre
  3. Loudness
  4. Amplitude
Show answer

Correct answer: (a) Frequency

The higher the frequency the higher the pitch.

89.Unit of frequency is: (PMC MDCAT 2022)

  1. Hertz
  2. decibel
  3. ampere
  4. radian
Show answer

Correct answer: (a) Hertz

Frequency is measured in hertz, one cycle a second.

90.The horizontal distance travelled by wave during one complete cycle is called (NUMS MDCAT 2022)

  1. Frequency
  2. Wavelength
  3. Amplitude
  4. Time period
Show answer

Correct answer: (b) Wavelength

The distance covered in one complete cycle is the wavelength.

91.Loudness of the sound is directly rotated to: (NUMS MDCAT 2022)

  1. Intensity of sound
  2. Frequency of sound
  3. Wavelength of sound
  4. Pitch of sound
Show answer

Correct answer: (a) Intensity of sound

Loudness follows the intensity, which is the energy carried each second through unit area.

92.Water waves are: (PMC MDCAT 2022)

  1. Longitudinal waves
  2. Complex waves
  3. Transverse waves
  4. Both longitudinal and transverse wave
Show answer

Correct answer: (d) Both longitudinal and transverse wave

A water particle moves in a circle, so the wave is part transverse and part longitudinal.

93.Example of mechanical waves is: (PMC MDCAT 2022)

  1. Transverse wave
  2. Longitudinal wave
  3. Both transverse and longitudinal wave
  4. Compressional waves
Show answer

Correct answer: (c) Both transverse and longitudinal wave

Mechanical waves may be transverse, as on a rope, or longitudinal, as in sound.

94.Sound waves are considered as ____ waves: (PMC MDCAT 2022)

  1. Compressional
  2. Transverse
  3. Longitudinal
  4. Shock
Show answer

Correct answer: (c) Longitudinal

The air moves to and fro along the direction the sound travels.

95.Speed of sound does not depend on: (PMC MDCAT 2022)

  1. Pressure
  2. Density
  3. Adiabatic Index
  4. Amplitude
Show answer

Correct answer: (a) Pressure

Raising the pressure raises the density in the same proportion, so $\sqrt{\gamma P/\rho}$ is unchanged.

96.The speed of sound cannot be greater than: (PMC MDCAT 2022)

  1. Speed of shock wave
  2. Speed of light
  3. Speed of water wave
  4. Speed of sound in vacuum
Show answer

Correct answer: (b) Speed of light

Nothing carries a signal faster than light, and sound is far slower than that.

97.The increase in the speed of sound in air for each degree rise above 0°C is: (NUMS MDCAT 2022)

  1. 0.40 m/s
  2. 0.51 m/s
  3. 0.81 m/s
  4. 0.61 m/s
Show answer

Correct answer: (d) 0.61 m/s

Sound gains about $0.61\,\mathrm{m\,s^{-1}}$ for each degree above $0^{\circ}\mathrm{C}$.

98.The speed of sound in air does not depend on: (NUMS MDCAT 2022)

  1. Density of medium
  2. Pressure
  3. Temperature
  4. Moisture
Show answer

Correct answer: (b) Pressure

Raising the pressure raises the density in the same proportion, so the speed is unchanged.

99.When two ends of string are struck together simultaneously such that two troughs are traveling towards each other, than at reaching the centre of the string a _ is formed: (PMC MDCAT 2022)

  1. A higher amplitude wave
  2. A Lower amplitude wave
  3. Waves die immediately
  4. Troughs are converted to crests
Show answer

Correct answer: (a) A higher amplitude wave

Trough falls on trough, so the displacements add and the wave is twice as deep.

100.The distance between two consecutive nodes of a stationary wave is: (PMC MDCAT 2022)

  1. λ
  2. λ/2
  3. λ/4
  4. λ/6
Show answer

Correct answer: (b) λ/2

Consecutive nodes of a stationary wave are half a wavelength apart.

101.Stationary waves are produced by: (PMC MDCAT 2022)

  1. Reflection
  2. Interference
  3. Diffraction
  4. Rarefaction
Show answer

Correct answer: (b) Interference

Two identical waves travelling opposite ways interfere to give a stationary pattern.

102.Stationary waves cannot be produced in: (PMC MDCAT 2022)

  1. Water waves
  2. Finite ropes
  3. Sound waves
  4. None of the above.
Show answer

Correct answer: (d) None of the above.

Stationary waves form in water, on a rope and in air alike, so there is no exception.

103.The sound waves have no: (PMC MDCAT 2022)

  1. Frequency of the wave
  2. Energy
  3. Nodes
  4. Intensity
Show answer

Correct answer: (c) Nodes

A progressive sound wave carries no nodes; nodes belong to a stationary wave.

104.A pipe open at both ends resonates at a fundamental frequency fo. When one end is covered and the pipe is again made to resonate, the fundamental frequency is fc. Which of the following expressions describes the relationship between these two resonants? (PMC MDCAT 2022)

  1. fc = fo
  2. 2xfc = fo
  3. fc = 2fo
  4. none
Show answer

Correct answer: (b) 2xfc = fo

An open pipe sounds $v/2L$ and a closed one $v/4L$, so the open note is twice the closed.

105.When will the oscillations of a pendulum stop in the absence of resistive forces? (MDCAT 2022)

  1. never
  2. after 10 minutes
  3. in 10 minutes
  4. immediately
Show answer

Correct answer: (a) never

With nothing to take its energy away the motion is undamped and continues indefinitely.

106.Reducing the mass $M$ of a suspended body to one fourth will change the frequency of oscillation to: (MDCAT 2022)

  1. one fourth
  2. double
  3. quadruple
  4. half
Show answer

Correct answer: (b) double

$f=\dfrac{1}{2\pi}\sqrt{k/m}$, so a quarter of the mass doubles the frequency.

107.Potential energy of a spring at the equilibrium position is: (PMC MDCAT 2022)

  1. Zero
  2. Infinite
  3. Maximum
  4. Information is Insufficient
Show answer

Correct answer: (a) Zero

At the equilibrium position the spring is unstretched, so it stores nothing.

108.Two springs having force constants in the ratio of 3:4, both the springs are stretched by equal force F, if elongation in first spring is x then elongation in the second spring is: (PMC MDCAT 2022)

  1. 3x
  2. 4x
  3. 3x/4
  4. 4x/3
Show answer

Correct answer: (c) 3x/4

$x=F/k$, so the stiffer spring stretches less, in the ratio $3/4$.

109.Kinetic energy of an oscillating simple pendulum at the equilibrium position is: (PMC MDCAT 2022)

  1. Maximum
  2. Minimum
  3. Zero
  4. Information insufficient
Show answer

Correct answer: (a) Maximum

The bob moves fastest as it passes through the mean position.

110.If the period of oscillation of man (M) suspended from a spring is 1s, then the period of 16M will be: (NUMS MDCAT 2022)

  1. 1s
  2. 2s
  3. 3s
  4. 4s
Show answer

Correct answer: (d) 4s

$T$ goes as $\sqrt{m}$, so sixteen times the mass gives four times the period.

Thermodynamics

111.Thermodynamics is that branch of physics in which we study the: (MDCAT 2022)

  1. relations between heat and mechanical energies
  2. relations between heat and internal energies only
  3. relations between chemical and mechanical energies
  4. relations between kinetic and potential energies
Show answer

Correct answer: (a) relations between heat and mechanical energies

Thermodynamics is about the exchange between thermal energy and mechanical work.

112.The temperature of a given mass of a gas is changed from $150^\circ$C to $300^\circ$C during an isobaric process. The volume of the gas will become: (MDCAT 2022)

  1. half
  2. double
  3. the same
  4. less than double
Show answer

Correct answer: (d) less than double

Volume goes as the absolute temperature, and $573/423\approx1.35$, which is less than twice.

113.The thermodynamic process during which the pressure is kept constant is called: (NUMS MDCAT 2022)

  1. Isochoric process
  2. Adiabatic proms
  3. Isobaric proem
  4. Isothermal proem
Show answer

Correct answer: (c) Isobaric proem

A change at constant pressure is isobaric.

114.When a gas expands isothermally, the product of its pressure and volume during the process is: (MDCAT 2022)

  1. not constant
  2. constant
  3. zero
  4. proportional to entropy
Show answer

Correct answer: (b) constant

At constant temperature $PV=nRT$ is fixed, which is Boyle's law.

115.First law of thermodynamics is based on: (NUMS MDCAT 2022)

  1. Law of conservation of momentum
  2. Law of conservation of mass
  3. Law of conservation of charge
  4. Law of conservation of energy
Show answer

Correct answer: (d) Law of conservation of energy

The first law is the conservation of energy written for heat and work.

116.The specific heat of a gas in adiabatic process is: (PMC MDCAT 2022)

  1. Zero
  2. Infinite
  3. Negative
  4. Remains constant
Show answer

Correct answer: (a) Zero

No heat is exchanged in an adiabatic change, so the heat per degree is zero.

117.Molar heat capacity at constant pressure is given by: (PMC MDCAT 2022)

  1. dQ/dV
  2. dQ/dT
  3. dU/dT
  4. dU/dV
Show answer

Correct answer: (b) dQ/dT

Molar heat capacity is the heat needed per mole for each degree of temperature rise.

118.Given that the Cv of a gas is 8 J/K mol, calculate the change in heat for dT=50K of 2 mole gas? (PMC MDCAT 2022)

  1. 800J
  2. 1631.4J
  3. 1700J
  4. 1800J
Show answer

Correct answer: (a) 800J

$Q=nC_v\Delta T=2\times8\times50$, which is $800\,\mathrm{J}$.

119.Molar heat capacity at constant volume is given by: (PMC MDCAT 2022)

  1. dQ/dN
  2. dQ/dP
  3. dU/dT
  4. dU/dV
Show answer

Correct answer: (c) dU/dT

At constant volume no work is done, so the heat per mole per degree is $dU/dT$.

120.Heat capacity is defined as _______ required to change the temperature of substance by_______ (PMC MDCAT 2022)

  1. Momentum, 1 degree C
  2. Heat, 1 degree C
  3. Heat, 2 degree C
  4. Work, 2 degree C
Show answer

Correct answer: (b) Heat, 1 degree C

Heat capacity is the heat needed to raise the temperature of the body by one degree.

121.Molar heat capacity is defined as heat required to raise the temperature by 1 degree of ____ substance. (PMC MDCAT 2022)

  1. 2 mole
  2. 2 kg
  3. 1 kg
  4. 1 mole
Show answer

Correct answer: (d) 1 mole

Molar heat capacity is the heat needed to raise one mole by one degree.

122.Specific heat of gas in isothermal process is: (PMC MDCAT 2022)

  1. Infinite
  2. Zero
  3. Negative
  4. Remain constant
Show answer

Correct answer: (a) Infinite

Heat is taken in with no rise in temperature, so the heat per degree is unbounded.

123.Unit of heat capacity is: (PMC MDCAT 2022)

  1. J/K
  2. J/K.mole
  3. J/K.kg
  4. Joule
Show answer

Correct answer: (a) J/K

Heat capacity is heat per degree, that is joules per kelvin.

124.For a monatomic ideal gas of 3 mole, Cp -Cv is: (PMC MDCAT 2022)

  1. R/3
  2. 3/2 R
  3. 2R
  4. 3R
Show answer

Correct answer: (d) 3R

$C_p-C_v=R$ for each mole, so for three moles it is $3R$.

125.The value of Cp and Cv is the same for: (PMC MDCAT 2022)

  1. He
  2. Ar
  3. Aluminium
  4. Neon
Show answer

Correct answer: (c) Aluminium

A solid barely changes volume on heating, so it does almost no work and its two heat capacities are the same.

126.If Cp = 20 J/mol.K then for 1 mole gas we get Cv= _______. You can use Cp/Cv = 1.7. (PMC MDCAT 2022)

  1. 10.6 J/K.mole
  2. 2.7 J/K.mole
  3. 13 J/K.mole
  4. 11.7 J/K.mole
Show answer

Correct answer: (d) 11.7 J/K.mole

$C_v=C_p/\gamma=20/1.7$, about $11.7\,\mathrm{J\,mol^{-1}\,K^{-1}}$.

127.Cp for monatomic gas in terms of R is: (PMC MDCAT 2022)

  1. 3/5 R
  2. 5/3 R
  3. 5/4 R
  4. 5/2 R
Show answer

Correct answer: (d) 5/2 R

For a monatomic gas $C_v=\tfrac32R$, so $C_p=\tfrac52R$.

128.For a monatomic ideal gas of 6 mole Cp/Cv: (PMC MDCAT 2022)

  1. 1.4
  2. 1.67
  3. 5
  4. 3
Show answer

Correct answer: (b) 1.67

For a monatomic gas $\gamma=\tfrac52R/\tfrac32R$, that is $1.67$, whatever the amount.

129.Cp = 49 J/K.mole and Cv= 35 J/K,mol then what type of gas Is this? (PMC MDCAT 2022)

  1. Diatomic
  2. Monatomic
  3. Triatomic
  4. Nonlinear-triatomic
Show answer

Correct answer: (a) Diatomic

$C_p-C_v=14$, about $R$, and $C_p/C_v=1.4$, which is the value for a diatomic gas.

Electrostatics

130.Which one of the following statements is true? (MDCAT 2022)

  1. the electrostatic force obeys the inverse square law while the gravitational force does not
  2. both the gravitational force and the electrostatic force are repulsive in nature
  3. the gravitational force is much weaker than the electrostatic force
  4. neither force obeys the inverse square law
Show answer

Correct answer: (c) the gravitational force is much weaker than the electrostatic force

Both are inverse square forces, but between two protons gravity is weaker by some $10^{36}$ times.

131.The Coulomb constant depends upon the: (MDCAT 2022)

  1. nature of the medium
  2. system of units
  3. type of charge
  4. nature of the medium and the system of units
Show answer

Correct answer: (d) nature of the medium and the system of units

$k=1/4\pi\varepsilon$ carries the permittivity of the medium, and its number depends on the units used.

132.The property of material due to which it attracts or repels other objects is: (PMC MDCAT 2022)

  1. Friction
  2. Velocity
  3. Acceleration
  4. Charge
Show answer

Correct answer: (d) Charge

That property is electric charge.

133.Which of the following forces are only attractive? (PMC MDCAT 2022)

  1. Electrostatic forces
  2. Gravitational forces
  3. Magnetic forces
  4. Forces between same poles of magnet
Show answer

Correct answer: (b) Gravitational forces

Gravitation pulls and never pushes; electric and magnetic forces do both.

134.When two positive charge particles move toward each other In opposite directions: (PMC MDCAT 2022)

  1. repulsion occurs
  2. attraction occurs
  3. Nothing will happen
  4. Charge will be neutralized
Show answer

Correct answer: (a) repulsion occurs

Like charges repel, so they push each other apart.

135.A charged particle is moving in a uniform electric field. For the motion of the particle due to the field, which quantity has a constant non-zero value? (MDCAT 2022)

  1. acceleration
  2. displacement
  3. rate of change of acceleration
  4. velocity
Show answer

Correct answer: (a) acceleration

A uniform field gives a constant force, so the acceleration $qE/m$ is constant.

136.When a charge gets influenced by its surrounding, it has entered: (PMC MDCAT 2022)

  1. An electric field
  2. A gravitational field
  3. Thermal field
  4. Closed field
Show answer

Correct answer: (a) An electric field

The region round a charge in which another charge feels a force is the electric field.

137.The force per unit charge is called: (PMC MDCAT 2022)

  1. Electric Force
  2. Electric Flux
  3. Electric Potential
  4. Electric Intensity
Show answer

Correct answer: (d) Electric Intensity

Force per unit charge is the electric field intensity.

138.Which of the following could not be the units of electric intensity? (PMC MDCAT 2022)

  1. Joule per coulomb per meter
  2. Joule per coulomb
  3. Volt per meter
  4. Newton per coulomb
Show answer

Correct answer: (b) Joule per coulomb

Joules per coulomb is the volt, that is potential, not field.

139.Direction of electric force and electric field intensity for a positive charge is: (PMC MDCAT 2022)

  1. Parallel to each other
  2. Perpendicular to each other
  3. Opposite to each other
  4. Random
Show answer

Correct answer: (a) Parallel to each other

The field is defined as the force on unit positive charge, so for a positive charge the two are along each other.

140.Electric field intensity is: (NUMS MDCAT 2022)

  1. Force per unit mass
  2. Force per unit tesla
  3. Force per unit charge
  4. Force per unit watt
Show answer

Correct answer: (c) Force per unit charge

Field intensity is the force on unit positive charge.

141.The flux through a surface will be zero when angle between E and △A is: (PMC MDCAT 2022)

  1. 90o
  2. 60o
  3. 30o
  4. 0o
Show answer

Correct answer: (a) 90o

Flux is $EA\cos\theta$, which vanishes when the field lies along the surface.

142.Charge inside conductor is: (PMC MDCAT 2022)

  1. Possible
  2. Can be greater than zero
  3. Zero
  4. Negative always
Show answer

Correct answer: (c) Zero

Charge on a conductor sits on its outer surface, so the interior encloses none.

143.The number of field lines passing through a certain element of area is known as: (PMC MDCAT 2022)

  1. Electric flux through that area
  2. Electric current through that area
  3. voltage through that area
  4. Amperes through that area
Show answer

Correct answer: (a) Electric flux through that area

The number of field lines crossing an area is the electric flux through it.

144.The electric flux through a closed surface depends upon the: (PMC MDCAT 2022)

  1. Size of the surface
  2. Shape of the surface
  3. Position of charge enclosed in the surface
  4. Magnitude of charge enclosed in the surface
Show answer

Correct answer: (d) Magnitude of charge enclosed in the surface

By Gauss’s law the flux out of a closed surface depends only on the charge inside it.

145.The electric flux through the surface of the sphere is directly proportional to the: (PMC MDCAT 2022)

  1. Surface area of the sphere
  2. Radius of the sphere
  3. Charge at the centre of the sphere
  4. Nature of charge
Show answer

Correct answer: (c) Charge at the centre of the sphere

By Gauss’s law the flux out of a closed surface is the enclosed charge over $\varepsilon_0$.

146.Electric Flux through the surface of a sphere which has constant charge at its centre depends on: (PMC MDCAT 2022)

  1. The radius of the sphere
  2. The surface area of the sphere
  3. The amount of charge inside the sphere
  4. The amount of charge outside the sphere
Show answer

Correct answer: (c) The amount of charge inside the sphere

By Gauss’s law only the enclosed charge matters, not the size of the surface.

147.The flux through a surface will be minimum when angle between E and △A is: (PMC MDCAT 2022)

  1. 90°
  2. 60°
  3. 30°
  4. 0o
Show answer

Correct answer: (a) 90°

Flux is $EA\cos\theta$, which falls to zero when the field lies along the surface.

148.Change in P.E per unit charge in the electric field is: (PMC MDCAT 2022)

  1. Electric potential
  2. Power
  3. K.E
  4. Work done
Show answer

Correct answer: (a) Electric potential

The change in potential energy per unit charge is the potential difference.

149.Electric potential determines the flow of? (PMC MDCAT 2022)

  1. Atom
  2. Molecule
  3. Compound
  4. Charge
Show answer

Correct answer: (d) Charge

Charge flows from a point of higher potential to one of lower potential.

150.The change in potential energy per unit charge between two points in an electric field is called: (PMC MDCAT 2022)

  1. Potential difference
  2. Absolute potential
  3. Electric Intensity
  4. Permitivity
Show answer

Correct answer: (a) Potential difference

The change in potential energy per unit charge is the potential difference.

151.Electrical potential energy between two charges at distance “r” is given by: (PMC MDCAT 2022)

  1. (k*q1*q2)/r
  2. (k*q1*q2)/r2
  3. k*q1*q2
  4. k*q1*q2/2r
Show answer

Correct answer: (a) (k*q1*q2)/r

The mutual potential energy of two point charges is $kq_1q_2/r$.

152.Electric Potential which is measured with respect to the zero potential is called: (PMC MDCAT 2022)

  1. Absolute electric potential
  2. Change in K.E
  3. Change in potential energy
  4. Electric intensity
Show answer

Correct answer: (a) Absolute electric potential

Potential measured from infinity, where the potential is taken as zero, is the absolute potential.

153.A capacitor is charged with a battery and the energy stored is $U$. After disconnecting the battery, another capacitor of the same capacity is connected in parallel to the first one. The energy stored in each capacitor is: (MDCAT 2022)

  1. $U/2$
  2. $U/4$
  3. $U$
  4. $2U$
Show answer

Correct answer: (b) $U/4$

The charge is shared equally, and $E=Q^2/2C$ with half the charge is a quarter of the energy.

154.A capacitor of capacitance $C$ has a charge $Q$ and stored energy $W$. If the charge is increased to $2Q$, the stored energy will be: (MDCAT 2022)

  1. $2W$
  2. $4W$
  3. $W/4$
  4. $W/2$
Show answer

Correct answer: (b) $4W$

$E=Q^2/2C$ goes as the square of the charge.

155.The device used to store a charge is called: (PMC MDCAT 2022)

  1. Electric box
  2. Capacitor
  3. Inductor
  4. Transistor
Show answer

Correct answer: (b) Capacitor

A capacitor stores charge, and with it energy.

156.In the combination of capacitors in series, the capacitors are connected: (PMC MDCAT 2022)

  1. Parallel
  2. side by side
  3. Up and down
  4. In circle only
Show answer

Correct answer: (b) side by side

Capacitors in series are joined end to end, so the same charge passes through all of them.

157.In parallel plate capacitor Capacitance depends on: (PMC MDCAT 2022)

  1. Charge
  2. Electric field
  3. Voltage
  4. Cross-sectional area
Show answer

Correct answer: (d) Cross-sectional area

$C=\varepsilon A/d$ carries the area and the separation, not the charge or the voltage.

158.Parallel combination of two capacitor C1 and C2 Is: (PMC MDCAT 2022)

  1. C1+ C2
  2. (C1)(C2)
  3. (C1C2)/(C1+C2)
  4. C1/C2
Show answer

Correct answer: (a) C1+ C2

Capacitors in parallel share the same voltage, so their capacitances add.

159.Energy stored in a capacitor is given by: (NUMS MDCAT 2022)

  1. E = ½ cv^2
  2. E.2 cv^2
  3. E . cv^2
  4. E = 2 cv^2
Show answer

Correct answer: (a) E = ½ cv^2

The stored energy is $\tfrac12CV^2$.

160.Q.64 It stores electrical potential energy: (NUMS MDCAT 2022)

  1. Capacitor
  2. Conductor
  3. Inductor
  4. Generator
Show answer

Correct answer: (a) Capacitor

A capacitor stores charge and with it electrical potential energy.

Current Electricity

161.The flow of charges produce: (PMC MDCAT 2022)

  1. Current only
  2. Magnetic field only
  3. Electric field only
  4. All of the above
Show answer

Correct answer: (d) All of the above

Moving charge is a current, and it carries both an electric and a magnetic field with it.

162.The SI unit of charge is: (PMC MDCAT 2022)

  1. Newton
  2. Coulomb
  3. Pascal
  4. Ampere
Show answer

Correct answer: (b) Coulomb

Charge is measured in coulombs.

163.____ potential difference is required for establishing steady current? (PMC MDCAT 2022)

  1. Minimum
  2. Constant
  3. Maximum
  4. Varying
Show answer

Correct answer: (b) Constant

A steady current needs a steady potential difference to drive it.

164.SI Unit of current is ? (PMC MDCAT 2022)

  1. Ampere
  2. Volt
  3. Joules
  4. Watt
Show answer

Correct answer: (a) Ampere

Current is measured in amperes.

165.Electric current may be defined as: (PMC MDCAT 2022)

  1. Rate of flow of charge
  2. Rate of flow of momentum
  3. Rate of flow of power
  4. Rate of flow of energy
Show answer

Correct answer: (a) Rate of flow of charge

Current is the charge passing a point each second.

166.Steady current does not change with respect to _____ (PMC MDCAT 2022)

  1. conductor
  2. source
  3. time
  4. potential difference
Show answer

Correct answer: (c) time

A steady current is one whose value does not change with time.

167.Current is ______ physical quantity (PMC MDCAT 2022)

  1. scalar quantity
  2. vector quantity
  3. variable quantity
  4. constant quantity
Show answer

Correct answer: (a) scalar quantity

Current has a direction of flow but adds as an ordinary number, so it is a scalar.

168._______ is a source of electrical energy having fixed polarity and terminals. (PMC MDCAT 2022)

  1. Motor
  2. Metals
  3. Battery
  4. Generator
Show answer

Correct answer: (c) Battery

A battery has a fixed positive and negative terminal.

169.Calculate the work done in a resistor of 20 ohm carrying 5A of current in 3 hours? (PMC MDCAT 2022)

  1. 1 kWh
  2. 1.5 kWh
  3. 2 kWh
  4. 3 kWh
Show answer

Correct answer: (b) 1.5 kWh

$P=I^2R=25\times20=500\,\mathrm{W}$, and $500\times3$ watt hours is $1.5\,\mathrm{kWh}$.

170.Basically a potentiometer is a device for: (PMC MDCAT 2022)

  1. Comparing two voltage
  2. Measuring current
  3. Comparing two currents
  4. Measuring voltage
Show answer

Correct answer: (a) Comparing two voltage

A potentiometer balances one emf against another, so it compares voltages without drawing current.

171.Which of the following statements is true? (PMC MDCAT 2022)

  1. Power is proportional to voltage only
  2. Power is proportional to current only
  3. Power is neither proportional to voltage nor to the current
  4. Power is proportional to both the voltage and current
Show answer

Correct answer: (d) Power is proportional to both the voltage and current

$P=VI$, so it rises with either.

172.Ohm’s law is applicable to (PMC MDCAT 2022)

  1. Semiconductors
  2. Vacuum tubes
  3. Carbon resistors
  4. Conductors
Show answer

Correct answer: (d) Conductors

Ohm’s law holds for metallic conductors at constant temperature; semiconductors and valve tubes are non-ohmic.

173.In series circuit, current remains? (PMC MDCAT 2022)

  1. Same
  2. Different
  3. Variable
  4. Zero
Show answer

Correct answer: (a) Same

There is only one path in a series circuit, so the same current passes through every element.

174.In parallel voltage remains? (PMC MDCAT 2022)

  1. Same
  2. Different
  3. Variable
  4. Zero
Show answer

Correct answer: (a) Same

Elements in parallel are connected across the same two points, so they share the same voltage.

175.A current of 16 amperes divides between two branches in parallel of resistances 8 ohms and 12 ohms respectively. The current in each branch is: (PMC MDCAT 2022)

  1. 6.4 a,6.9 a
  2. 6.4 a, 9.6 a
  3. 4.6 a,6.9 a
  4. 4.6 a,9.6 a
Show answer

Correct answer: (b) 6.4 a, 9.6 a

The current divides in inverse ratio to the resistances, giving $9.6\,\mathrm{A}$ in the $8\,\Omega$ branch and $6.4\,\mathrm{A}$ in the other.

176.The circuit which gives continuously varying potential is called: (PMC MDCAT 2022)

  1. Complex network
  2. Wheatstone bridge
  3. Potential divider
  4. Galvanometer
Show answer

Correct answer: (c) Potential divider

A potential divider taps off any fraction of the supply voltage as the slider is moved.

177.The sensitivity of a potentiometer can be Increased by ____ (PMC MDCAT 2022)

  1. Increasing the e.m.f of the primary coil
  2. Increasing the Potential gradient
  3. lncreasing the length of the potentiometer wire
  4. Decreasing the length of the potentiometer wire
Show answer

Correct answer: (c) lncreasing the length of the potentiometer wire

A longer wire gives a smaller potential gradient, so a given voltage is balanced over a greater length.

178.Which one of the following is a disadvantage of a potentiometer over a voltmeter? (PMC MDCAT 2022)

  1. It can measure internal resistance of a cell
  2. It can measure the e.m.f. of a cell
  3. It is heavy and not portable
  4. It can measure accurately very small pd. of the microvolt
Show answer

Correct answer: (c) It is heavy and not portable

The potentiometer is accurate but bulky, and it must be set up and balanced for each reading.

179.The SI Unit for resistance is? (PMC MDCAT 2022)

  1. Ohm
  2. Ampere
  3. Watt
  4. Volts
Show answer

Correct answer: (a) Ohm

Resistance is measured in ohms.

180.__________ relationship exists between current and voltage in terms of Ohm’s law: (PMC MDCAT 2022)

  1. Non linear
  2. Varying
  3. Linear
  4. Alternating
Show answer

Correct answer: (c) Linear

$V=IR$ with $R$ constant is the equation of a straight line.

181.Ohm’s Law is applicable only when temperature is: (PMC MDCAT 2022)

  1. changing
  2. absolute zero
  3. constant
  4. decreasing
Show answer

Correct answer: (c) constant

Resistance changes with temperature, so Ohm’s law holds only while the temperature is held.

182.Ohm’s law is valid when the temperature of conductor Is : (PMC MDCAT 2022)

  1. Very low
  2. Very high
  3. Varying
  4. Constant
Show answer

Correct answer: (d) Constant

Resistance changes with temperature, so the law holds only while the temperature is held constant.

183.Correct form of ohm’s law (PMC MDCAT 2022)

  1. I = VR
  2. V = I/R
  3. V = IR
  4. R= IV
Show answer

Correct answer: (c) V = IR

Ohm’s law is $V=IR$.

184.In order to achieve high accuraccy, the slide wire of a potentiometer should be (PMC MDCAT 2022)

  1. As long as possible
  2. As short as possible
  3. Neither too small not to large
  4. Very thick
Show answer

Correct answer: (a) As long as possible

A long wire gives a small potential gradient, so the balance point can be read finely.

185.Q.65 A magnitude of the current in metals is proportional to the applied voltage as long as temperature of conductor is kept constant. It is statement of: (NUMS MDCAT 2022)

  1. Joule's law
  2. Gauss's law
  3. Ohm, law
  4. Ampere's law
Show answer

Correct answer: (c) Ohm, law

That is Ohm’s law.

186.The resistance of a conductor does not depend on which of the following? (MDCAT 2022)

  1. area of cross-section
  2. resistivity
  3. length
  4. mass
Show answer

Correct answer: (d) mass

$R=\rho L/A$ has no mass in it.

187.What do substances whose resistance decreases with a rise in temperature have? (MDCAT 2022)

  1. a high temperature coefficient
  2. a negative temperature coefficient
  3. a positive temperature coefficient
  4. a zero temperature coefficient
Show answer

Correct answer: (b) a negative temperature coefficient

A falling resistance means the temperature coefficient of resistance is negative, as it is for semiconductors.

188.The resistance of a conductor at absolute zero ( OK) is: (PMC MDCAT 2022)

  1. Almost zero
  2. Almost infinite
  3. No prediction at all
  4. May increase or decrease
Show answer

Correct answer: (a) Almost zero

With the lattice almost still there is nothing to scatter the electrons, so the resistance falls away.

189.Resistance of a conductor depends upon: (PMC MDCAT 2022)

  1. Temperature
  2. Nature of a conductor
  3. Length
  4. Color
Show answer

Correct answer: (c) Length

$R=\rho L/A$: the longer the conductor the greater its resistance.

190.Resistivity of a substance Is defined as the resistance of a _____ of that substance. (PMC MDCAT 2022)

  1. meter
  2. meter square
  3. meter cube
  4. centimeter
Show answer

Correct answer: (b) meter square

Resistivity is the resistance of a cube of the material of unit side, measured between opposite faces.

191.The specific resistance of a conductor Increases with: (PMC MDCAT 2022)

  1. Increase in temperature
  2. increase in cross-sectional area
  3. Decrease in length
  4. decrease In cross-sectional area
Show answer

Correct answer: (a) Increase in temperature

Heating makes the lattice vibrate more and scatter the electrons, so the resistivity rises.

192.Q.66 The resistance of pure metal increases with: (NUMS MDCAT 2022)

  1. Increase in temperature
  2. Increase in pressure
  3. Decrease in temperature
  4. Decrease in pressure
Show answer

Correct answer: (a) Increase in temperature

A metal grows more resistive as it is heated.

193.A low voltage supply of e.m.f. 20 V and internal resistance $1.5\ \Omega$ is used to work a heater of resistance $6.5\ \Omega$ in a fish tank. What is the power delivered to the water in the fish tank? (MDCAT 2022)

  1. 41 W
  2. 50 W
  3. 53 W
  4. 62 W
Show answer

Correct answer: (a) 41 W

$I=20/(1.5+6.5)=2.5$ A, so $P=I^2R=(2.5)^2(6.5)\approx41$ W.

194.The terminal potential difference of a battery is greater than its emf when: (PMC MDCAT 2022)

  1. The internal resistance of a battery is infinite
  2. The internal resistance of a battery is zero
  3. The battery is being charged
  4. The battery is discharged
Show answer

Correct answer: (c) The battery is being charged

When current is driven into the cell the drop across the internal resistance adds to the emf.

195.Terminal potential difference of a cell: (PMC MDCAT 2022)

  1. Increases with increase in its internal resistance
  2. Decreases with increase in its internal resistance
  3. Its independent of its internal resistance
  4. Varies exponentially with resistance
Show answer

Correct answer: (b) Decreases with increase in its internal resistance

The greater the internal resistance the more of the emf is spent inside the cell.

196.Which equation represents the maximum output power of source? (PMC MDCAT 2022)

  1. P = VI
  2. P = I2R
  3. P = V2/R
  4. P = E2/4R
Show answer

Correct answer: (d) P = E2/4R

Most power reaches the load when its resistance matches the internal one, and then $P=E^2/4R$.

Electromagnetism

197.The source of a magnetic field is: (MDCAT 2022)

  1. an isolated magnetic pole
  2. a static electric charge
  3. a current loop
  4. a stationary magnet only
Show answer

Correct answer: (c) a current loop

Moving charge is what makes a magnetic field, and the current loop is its simplest source.

198.Tesla is unit of ____ per unit area: (PMC MDCAT 2022)

  1. Magnetic field lines
  2. Electric field lines
  3. Optical field lines
  4. Gravitational field lines
Show answer

Correct answer: (a) Magnetic field lines

One tesla is one weber of flux through each square metre.

199.If we cut a magnet in half then both magnets are now (PMC MDCAT 2022)

  1. Monopole
  2. Dipole
  3. Quadrupole
  4. magnetsim is lost
Show answer

Correct answer: (b) Dipole

A magnet cut in two gives two magnets, each with its own north and south pole.

200.Magnetic field inside a long solenoid is: (PMC MDCAT 2022)

  1. Varying with radial distance
  2. Uniform
  3. Zero
  4. Not enough Information
Show answer

Correct answer: (b) Uniform

Inside a long solenoid the field is uniform and along the axis.

201.When a bar magnet is broken from middle, the broken pieces will have: (PMC MDCAT 2022)

  1. North pole only
  2. Sooth pole only
  3. Both south and north poles
  4. Magnetism will be removed
Show answer

Correct answer: (c) Both south and north poles

A magnet cut in two gives two magnets, each with its own pair of poles.

202.The study of magnets is called: (PMC MDCAT 2022)

  1. Electromagnetism
  2. Magnetism
  3. Electrostatics
  4. Current electricity
Show answer

Correct answer: (b) Magnetism

The study of magnets and their fields is magnetism.

203.If the current in a wire is doubled then magnetic field would be: (PMC MDCAT 2022)

  1. halved
  2. remain same
  3. triple
  4. double
Show answer

Correct answer: (d) double

The field of a current is proportional to it, so twice the current gives twice the field.

204.When two magnets come closer such that same poles face each other than field lines: (PMC MDCAT 2022)

  1. Intersect
  2. Repel
  3. Come closer
  4. Nothing will happen
Show answer

Correct answer: (b) Repel

Field lines never cross, so like poles brought together push their lines apart.

205.Which surface has the greater magnetic flux in the same magnetic field, each having an area of $1\ \mathrm{m^2}$? (MDCAT 2022)

  1. circular
  2. rectangular
  3. square
  4. the flux is independent of the shape
Show answer

Correct answer: (d) the flux is independent of the shape

$\Phi=BA\cos\theta$ depends on the area and its orientation, not on the shape of the boundary.

206.The magnetic flux is a _______ quantity: (PMC MDCAT 2022)

  1. Scalar
  2. Vector
  3. Vector In some cases
  4. Scalar In some cases
Show answer

Correct answer: (a) Scalar

Flux is the scalar product of flux density and area, so it is a scalar.

207.Magnetic flux is defined as: (PMC MDCAT 2022)

  1. Magnetic field lines passing over a volume
  2. Magnetic field lines passing through a surface
  3. Current passing through volume
  4. current passing through surface
Show answer

Correct answer: (b) Magnetic field lines passing through a surface

Flux is the number of field lines crossing a surface.

208.The magnetic flux density is: (PMC MDCAT 2022)

  1. magnetic field lines per unit area
  2. magnetic field lines per unit volume
  3. electric field lines per unit area
  4. electric field lines per unit volume
Show answer

Correct answer: (a) magnetic field lines per unit area

Flux density is the flux crossing unit area held at right angles to the field.

209.Q.68 Magnetic flux is maximum when Angle between magnetic field and vector area is: (NUMS MDCAT 2022)

  1. 0°
  2. 90°
  3. 30°
  4. 45°
Show answer

Correct answer: (a) 0°

$\Phi=BA\cos\theta$ is greatest when the area vector lies along the field.

210.Electric forces change the magnitude and direction of velocity, while magnetic forces change the: (MDCAT 2022)

  1. magnitude only
  2. direction only
  3. magnitude and direction
  4. neither magnitude nor direction
Show answer

Correct answer: (b) direction only

The magnetic force is always perpendicular to the velocity, so it does no work and only turns the particle.

211.If electron and proton projected in a magnetic fleld simultaneously then _ _ _ _ will be deflected more: (PMC MDCAT 2022)

  1. Electron
  2. Proton
  3. Electron and proton both
  4. No effect
Show answer

Correct answer: (a) Electron

The force is the same but the electron is about two thousand times lighter, so it turns far more sharply.

212.When two positive and negative particles are moving opposite to each other in uniform magnetic field: (PMC MDCAT 2022)

  1. Deflection occurs
  2. Attraction occurs
  3. Repulsion occurs
  4. Nothing will happen
Show answer

Correct answer: (a) Deflection occurs

Opposite charges moving opposite ways feel forces the same way round, and both are deflected.

Electromagnetic Induction

213.A one metre long copper rod is moved with a speed of $20\ \mathrm{m\,s^{-1}}$ in a magnetic field of strength 0.6 tesla. What is the value of the induced emf? (MDCAT 2022)

  1. 10 V
  2. 12 V
  3. 14 V
  4. 16 V
Show answer

Correct answer: (b) 12 V

$\varepsilon=BvL=0.6\times20\times1=12$ V.

214.The unit of $\Delta\Phi/\Delta t$ can be written as: (MDCAT 2022)

  1. $\mathrm{N\,m\,A^{-2}\,s^{-1}}$
  2. $\mathrm{N\,m\,A\,s^{-2}}$
  3. $\mathrm{N\,m\,A^{-1}\,s^{-1}}$
  4. $\mathrm{N\,m\,A^{-2}\,s}$
Show answer

Correct answer: (c) $\mathrm{N\,m\,A^{-1}\,s^{-1}}$

The rate of change of flux is an emf, and $1\ \mathrm{V}=1\ \mathrm{J\,C^{-1}}=1\ \mathrm{N\,m\,A^{-1}\,s^{-1}}$.

215.A copper hoop is held in a vertical east-west plane in a uniform magnetic field whose field lines run along the north-south direction. The largest induced emf is produced when the hoop is: (MDCAT 2022)

  1. rotated about a north-south axis
  2. rotated about an east-west axis
  3. moved rapidly, without rotation, towards the east
  4. moved rapidly, without rotation, towards the south
Show answer

Correct answer: (b) rotated about an east-west axis

Turning about an east-west axis swings the plane of the hoop through the field and changes the flux fastest; the other motions leave the flux unchanged.

216.AC generator consists of __ poles: (PMC MDCAT 2022)

  1. 0
  2. 1
  3. 2
  4. 3
Show answer

Correct answer: (c) 2

The armature turns between a north and a south pole, so there are two.

217.The emf induced in a circuit according to Faraday’s law depends on the (PMC MDCAT 2022)

  1. Maximum magnetic flux
  2. Initial magnetic flux
  3. Change in magnetic flux
  4. The rate of change of magnetic flux
Show answer

Correct answer: (d) The rate of change of magnetic flux

Faraday’s law makes the emf equal to the rate at which the flux changes.

218.AC generators are similar to : (PMC MDCAT 2022)

  1. Transformers
  2. Inductors
  3. Capacitors
  4. Motor
Show answer

Correct answer: (d) Motor

A generator is a motor run backwards: turn the coil and it gives current instead of taking it.

219.AC generator cannot generate: (PMC MDCAT 2022)

  1. AC voltage
  2. High AC voltage
  3. DC voltage
  4. Low AC voltage
Show answer

Correct answer: (c) DC voltage

A rotating coil in a field gives an emf that reverses every half turn, so its output is alternating.

220.The mechanical energy of our hand used to push the magnet towards or away from the coil results into: (PMC MDCAT 2022)

  1. Heat energy
  2. Potential energy
  3. Electrical energy
  4. Mechanical energy
Show answer

Correct answer: (c) Electrical energy

The work done against the induced current appears as electrical energy in the coil.

221.AC generator converts ________ energy: (PMC MDCAT 2022)

  1. Mechanical to electrical
  2. Electrical to mechanical
  3. Electrical to heat
  4. Heat to electrical
Show answer

Correct answer: (a) Mechanical to electrical

A generator turns the work of rotating the coil into electrical energy.

222.When coil is rotated in magnetic field, the current produced is: (PMC MDCAT 2022)

  1. Constant
  2. Decrease
  3. Increase
  4. Continuously changing
Show answer

Correct answer: (d) Continuously changing

The flux through the coil changes from moment to moment, so the induced current does too.

223.The current produced by a moving coil is called: (PMC MDCAT 2022)

  1. Induced current
  2. Direct current
  3. Polarized current
  4. No current
Show answer

Correct answer: (a) Induced current

A current produced by a changing flux is an induced current.

224.The self inductance of a coil does not depend upon: (PMC MDCAT 2022)

  1. length
  2. current
  3. the number of turns
  4. the area of the coil
Show answer

Correct answer: (b) current

Self inductance depends on the turns, the area, the length and the core, not on the current flowing.

225.The working principle of the magnetic levitation train is: (MDCAT 2022)

  1. Faraday's law
  2. Planck's law
  3. Ohm's law
  4. Lenz's law
Show answer

Correct answer: (d) Lenz's law

The induced currents oppose the approaching magnets, and that repulsion is Lenz's law at work.

226.The negative sign in Lenz’s law indicates that the induced emf opposes the rate of change of: (PMC MDCAT 2022)

  1. Electric flux
  2. Magentic flux
  3. Electric field
  4. Magentic field
Show answer

Correct answer: (b) Magentic flux

The induced emf opposes the change of flux that produced it.

227.The Lenz’s law is used to find out the direction of (PMC MDCAT 2022)

  1. Current induced in circuit
  2. Potential energy
  3. Magnetic field
  4. Force
Show answer

Correct answer: (a) Current induced in circuit

Lenz’s law fixes the direction of the induced current.

228.Q.69 Lenz's law is based on the law of conservation of: (NUMS MDCAT 2022)

  1. Mass
  2. Energy
  3. Charge
  4. Momentum
Show answer

Correct answer: (b) Energy

If the induced current helped the change, energy would be created out of nothing.

229.In a transformer there is no ______ connection between the two coils, but they are ______ linked. (MDCAT 2022)

  1. magnetic, electrically
  2. electrical, magnetically
  3. magnetic, magnetically
  4. electrical, optically
Show answer

Correct answer: (b) electrical, magnetically

The two windings are insulated from each other and the flux in the core is what couples them.

230.Power loss in the actual transformer is due to: (PMC MDCAT 2022)

  1. Back emf
  2. Strong magnetic field
  3. Eddy currents
  4. Weak magnetic field
Show answer

Correct answer: (c) Eddy currents

Currents induced in the core itself waste energy as heat, which is why the core is laminated.

231.In step down transformer, current in secondary coil is ___ than current in primary coil: (PMC MDCAT 2022)

  1. Equal
  2. Less
  3. Greater
  4. Unchanged
Show answer

Correct answer: (c) Greater

Power is conserved, so a lower secondary voltage means a larger secondary current.

232.Transformer can convert _________ (PMC MDCAT 2022)

  1. Low DC voltage
  2. High DC voltage
  3. Battery voltage
  4. AC voltage
Show answer

Correct answer: (d) AC voltage

A transformer works on a changing flux, so only alternating voltage can be transformed.

233.Eddy currents flow in: (PMC MDCAT 2022)

  1. Open loops
  2. Closed loops
  3. Straight lines
  4. Vertlcal loops
Show answer

Correct answer: (b) Closed loops

Eddy currents circulate in closed loops within the body of the metal.

234.Q.71 Transformer works on the principle of: (NUMS MDCAT 2022)

  1. Half wave rectification
  2. Self-Induction
  3. Mutual Induction
  4. Full wave rectification
Show answer

Correct answer: (c) Mutual Induction

A changing flux in the primary induces an emf in the secondary, which is mutual induction.

Alternating Current

235.The direct exposure of sun light where ozone layer is depleted will cause: (PMC MDCAT 2022)

  1. Skin cancer
  2. Sugar
  3. Corona
  4. Sun burn
Show answer

Correct answer: (a) Skin cancer

The ozone layer absorbs the ultraviolet, and without it that radiation reaches the skin.

236.In amplitude modulation what remains the same: (PMC MDCAT 2022)

  1. Frequency of the wave
  2. Amplitude of the wave
  3. Wavelength of the wave
  4. Intensity of waves
Show answer

Correct answer: (a) Frequency of the wave

In amplitude modulation the carrier frequency is held and only the amplitude is varied.

237.In frequency modulation, which of the following property of the original signal does not change: (PMC MDCAT 2022)

  1. Pitch
  2. Frequency
  3. Wavelength
  4. Amplitude
Show answer

Correct answer: (d) Amplitude

In frequency modulation the amplitude of the carrier is held steady and only its frequency is varied.

238.Energy emitted in the form of visible radiation is called: (PMC MDCAT 2022)

  1. Light energy
  2. Sound energy
  3. Tidal energy
  4. Geothermal energy
Show answer

Correct answer: (a) Light energy

Radiation the eye can see is light.

239.The electromagnetic radiation which moves with high frequency will have _______ wavelength: (PMC MDCAT 2022)

  1. Short
  2. Long
  3. Unchanged
  4. Variable
Show answer

Correct answer: (a) Short

$c=f\lambda$ is fixed, so a high frequency goes with a short wavelength.

240.Microwave is: (PMC MDCAT 2022)

  1. An electromagnetic wave
  2. Sound wave
  3. Longitudinal wave
  4. Standing wave
Show answer

Correct answer: (a) An electromagnetic wave

Microwaves lie between the radio waves and the infrared in the electromagnetic spectrum.

Electronics

241.Transistors can be used as: (PMC MDCAT 2022)

  1. Half-wave rectifier
  2. Full-wave rectifier
  3. Photocell
  4. Switch
Show answer

Correct answer: (d) Switch

A transistor can be driven fully on or fully off, which makes it a switch.

242.Which of the following rectifier uses wheatstone bridge to rectify signal: (PMC MDCAT 2022)

  1. Half wave
  2. Full wave
  3. Bridge
  4. Both half and full wave
Show answer

Correct answer: (c) Bridge

A bridge rectifier is four diodes in a Wheatstone arrangement.

243.Most widely used rectifier is: (PMC MDCAT 2022)

  1. Half wave rectifier
  2. Full wave rectifier
  3. Bridge rectifier
  4. Loop rectifier
Show answer

Correct answer: (c) Bridge rectifier

The bridge rectifier needs no centre-tapped transformer, so it is the one usually used.

244.A full wave rectifier passes _________ into positive cycles: (PMC MDCAT 2022)

  1. Lower half cycle
  2. Upper half cycle
  3. Both lower and upper half cycles
  4. One quarter cycle
Show answer

Correct answer: (c) Both lower and upper half cycles

A full wave rectifier turns both half cycles the same way up.

245.Ripple factor of half wave rectifier Is: (PMC MDCAT 2022)

  1. 1.21
  2. 0.8
  3. 0.6
  4. 0.4
Show answer

Correct answer: (a) 1.21

The ripple factor of a half wave rectifier is $1.21$.

246.Q.72 A device that converts AC into DC is called: (NUMS MDCAT 2022)

  1. Diode
  2. Transistor
  3. Capacitor
  4. Inductor
Show answer

Correct answer: (a) Diode

A diode passes current one way only.

247.Q.73 The conversion of alternating current into direct current is called: (NUMS MDCAT 2022)

  1. Amplification
  2. Rectification
  3. Magnification
  4. Resolution
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Correct answer: (b) Rectification

That process is rectification.

Dawn of Modern Physics

248.The process of ejection of loosely bound electrons from a photosensitive surface by the absorption of photons is called: (MDCAT 2022)

  1. the Compton effect
  2. the photoelectric effect
  3. pair production
  4. black body radiation
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Correct answer: (b) the photoelectric effect

One photon gives its whole energy to one electron and ejects it, which is the photoelectric effect.

249.In a photoelectric effect experiment, the stopping potential is: (MDCAT 2022)

  1. the kinetic energy of the most energetic electron ejected
  2. the potential energy of the most energetic electron ejected
  3. the photon energy
  4. the electric potential that causes the electron current to vanish
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Correct answer: (d) the electric potential that causes the electron current to vanish

It is the reverse potential at which even the fastest photoelectron is turned back, so the current falls to zero.

250.Wave nature and particle nature of photon is linked by: (PMC MDCAT 2022)

  1. Rest mass of photon
  2. Wavelength of photon
  3. Light speed
  4. Momentum of photon
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Correct answer: (d) Momentum of photon

$p=h/\lambda$ ties the momentum of the particle to the wavelength of the wave.

251.The word radiation means: (PMC MDCAT 2022)

  1. To propagate
  2. stay at rest
  3. Mass less objects
  4. Charged object
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Correct answer: (a) To propagate

To radiate is to send energy out through space.

252.If the temperature of Sun is doubled, heat energy reached on earth become: (PMC MDCAT 2022)

  1. Three Times
  2. Sixteen Times
  3. Four Times
  4. Same
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Correct answer: (b) Sixteen Times

By Stefan’s law the power radiated goes as $T^4$, so twice the temperature is sixteen times the energy.

253.A body at temperature T radiates heat according to relation: (PMC MDCAT 2022)

  1. T2
  2. T4
  3. T-4
  4. T-3
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Correct answer: (b) T4

Stefan’s law gives the radiated power as proportional to the fourth power of the temperature.

254.Photons of energy 10.25 eV fall on the surface of the metal emitting photoelectrons of maximum kinetic energy 5.0 eV. What is the stopping voltage required for these electrons? (PMC MDCAT 2022)

  1. 10V
  2. 8V
  3. 5V
  4. 4V
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Correct answer: (c) 5V

The stopping potential is the maximum kinetic energy in electron volts, that is $5\,\mathrm{V}$.

255.Blackbody shows a ______ spectra: (PMC MDCAT 2022)

  1. Continuous
  2. Discrete
  3. Band
  4. Line
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Correct answer: (a) Continuous

A hot body radiates at every wavelength, so its spectrum is continuous.

256.Planck’s constant is analogous to: (PMC MDCAT 2022)

  1. Inertia
  2. Wave nature
  3. Angular momentum
  4. Linear momentum
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Correct answer: (c) Angular momentum

Planck’s constant has the units of energy times time, which are the units of angular momentum.

257.Among the following four spectral regions, which photon has the highest energy? (PMC MDCAT 2022)

  1. Infrared
  2. Violet
  3. Blue
  4. red
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Correct answer: (b) Violet

Energy is $hf$, and violet has the highest frequency of the four.

258.Planck constant is named after: (PMC MDCAT 2022)

  1. Einstein
  2. Newton
  3. Maxwell
  4. Max planck
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Correct answer: (d) Max planck

It is named after Max Planck, who introduced it in 1900.

259.The black body always __ radiations: (PMC MDCAT 2022)

  1. Emit
  2. Absorb
  3. Both Emit And Absorb
  4. Reflects
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Correct answer: (c) Both Emit And Absorb

A black body is a perfect absorber and, at the same temperature, a perfect emitter.

260.Photocell is based on: (PMC MDCAT 2022)

  1. Photoelectric effect
  2. Compton effect
  3. Photoluminescence
  4. Pair production
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Correct answer: (a) Photoelectric effect

Light falling on the cathode of a photocell frees electrons, which is the photoelectric effect.

Atomic Spectra

261.The line spectrum of the hydrogen atom contains spectral lines in the region of: (MDCAT 2022)

  1. ultraviolet
  2. infrared
  3. visible
  4. all of these
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Correct answer: (d) all of these

The Lyman series is ultraviolet, the Balmer series visible and the Paschen and later series infrared.

262.The speed of an electron in the first Bohr orbit is: (MDCAT 2022)

  1. $2.19\times10^{5}\ \mathrm{m\,s^{-1}}$
  2. $2.19\times10^{6}\ \mathrm{m\,s^{-1}}$
  3. $2.19\times10^{7}\ \mathrm{m\,s^{-1}}$
  4. $2.19\times10^{8}\ \mathrm{m\,s^{-1}}$
Show answer

Correct answer: (b) $2.19\times10^{6}\ \mathrm{m\,s^{-1}}$

The first orbit speed is about $2.19\times10^{6}\ \mathrm{m\,s^{-1}}$, roughly one hundredth of the speed of light.

263.X-ray is the reverse process of: (PMC MDCAT 2022)

  1. Pair production
  2. Compton effect
  3. Photoelectric effect
  4. Annihilation
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Correct answer: (c) Photoelectric effect

In the photoelectric effect a photon frees an electron; in X-ray production a stopped electron makes a photon.

264.Where does the energy lost by fast moving electron go: (PMC MDCAT 2022)

  1. Appears as photon
  2. Appears as electrom – positron pair
  3. Appears as its k.e.
  4. It vanishes
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Correct answer: (a) Appears as photon

A fast electron stopped suddenly gives up its energy as an X-ray photon.

265.Lasers are produced by: (PMC MDCAT 2022)

  1. Stimulated emission
  2. Spontaneous emission
  3. Absorption
  4. Random Absorption
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Correct answer: (a) Stimulated emission

A laser works by stimulated emission, which is what makes its light coherent.

266.Bright Lines in pattern shows: (PMC MDCAT 2022)

  1. Absorption
  2. Emission
  3. Reflection
  4. Free particle
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Correct answer: (b) Emission

Bright lines are made by atoms giving out photons, that is by emission.

267.When electron absorbs a photon and jumps to higher states it is called: (PMC MDCAT 2022)

  1. De-excitation
  2. Excitation
  3. Emission
  4. Conversion
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Correct answer: (b) Excitation

Absorbing a photon lifts the electron to a higher level, which is excitation.

268.X rays are also known as: (PMC MDCAT 2022)

  1. Low energy invisible photons
  2. High energy visible photons
  3. High energy invisible photons
  4. Low energy visible photons
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Correct answer: (c) High energy invisible photons

X-rays are photons far beyond the violet in energy, and the eye cannot see them.

269.Spectral lines is like a —– of absorbed or emission energy in a spectrum: (PMC MDCAT 2022)

  1. Charged Pattern
  2. Fingerprint Pattern
  3. Discharged Pattem
  4. Scattered Pattern
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Correct answer: (b) Fingerprint Pattern

Every element has its own set of lines, so the spectrum identifies it as a fingerprint would.

Nuclear Physics

270.For two down quarks total charge is: (PMC MDCAT 2022)

  1. -2/3 e
  2. -2 e
  3. -1 e
  4. -1/2 e
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Correct answer: (a) -2/3 e

A down quark carries $-\tfrac13e$, so two of them carry $-\tfrac23e$.

271.Naturally occuring fusion reaction source Is: (PMC MDCAT 2022)

  1. Moon
  2. Sun
  3. Earth
  4. satellite
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Correct answer: (b) Sun

Hydrogen fusing to helium is what keeps the Sun shining.

272.How many up quarks in proton: (PMC MDCAT 2022)

  1. 1
  2. 2
  3. 3
  4. 4
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Correct answer: (b) 2

A proton is two up quarks and one down quark.

273.Which particle has no charge (PMC MDCAT 2022)

  1. Electrons
  2. Proton
  3. Neutron
  4. Positron
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Correct answer: (c) Neutron

The neutron carries no charge.

274.It has been observed that thorium $^{234}_{90}\mathrm{Th}$ is transformed into protactinium $^{234}_{91}\mathrm{Pa}$ after the emission of a ______ particle. (MDCAT 2022)

  1. alpha
  2. beta
  3. gamma
  4. alpha and gamma together
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Correct answer: (b) beta

The mass number is unchanged and the atomic number rises by one, which is beta-minus decay.

275.When gamma photon is entered in nucleus it_ _ : (PMC MDCAT 2022)

  1. De-excite the nucleus
  2. excite the nucleus
  3. Scatter by nucleus
  4. No effect on nucleus
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Correct answer: (b) excite the nucleus

A gamma photon absorbed by a nucleus lifts it to a higher energy state.

276.C-14 decays by emitting a beta particle. After decay new element becomes: (PMC MDCAT 2022)

  1. C-13
  2. N-14
  3. 0-15
  4. O-16
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Correct answer: (b) N-14

Beta emission leaves the mass number alone and raises the atomic number by one, giving nitrogen-14.

277.Which radiation will be deflected more by magnetic fleld? (PMC MDCAT 2022)

  1. α-radiation
  2. β-radiation
  3. x-rays
  4. Electromagnetic radiation
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Correct answer: (b) β-radiation

A beta particle is far lighter than an alpha, so the same force bends it much more.

278.The half-life of strontium is 8.70 hours. Its decay constant is: (MDCAT 2022)

  1. $0.000022\ \mathrm{s^{-1}}$
  2. $45000\ \mathrm{s^{-1}}$
  3. $0.0022\ \mathrm{s^{-1}}$
  4. $0.22\ \mathrm{s^{-1}}$
Show answer

Correct answer: (a) $0.000022\ \mathrm{s^{-1}}$

$\lambda=0.693/T_{1/2}=0.693/(8.70\times3600)=2.2\times10^{-5}\ \mathrm{s^{-1}}$.

279.What is the relationshlp between the half life of a radioactive isotope and its wavelength? (PMC MDCAT 2022)

  1. they are equal in magnitude
  2. they are directly proportional
  3. they are inversely proportional
  4. No relation
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Correct answer: (d) No relation

Half life is a property of the nucleus and has nothing to do with any wavelength.

280.Q.75 A 32g radioactive element decays and remains 2g after 60 days. What is the half-life of radioactive element? (NUMS MDCAT 2022)

  1. 2 days
  2. 6 days
  3. 10 days
  4. 15 days
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Correct answer: (d) 15 days

From $32$ to $2\,\mathrm{g}$ is four half lives, and $60/4$ is $15$ days.

281.In water pipes _________ is used to detect leakages: (PMC MDCAT 2022)

  1. Radioisotope
  2. Light
  3. Current
  4. Heat
Show answer

Correct answer: (a) Radioisotope

A tracer added to the water shows up where it escapes from the buried pipe.

Other MDCAT past papers