MDCAT 2024 Physics

MDCAT 2024 Physics Past Paper MCQs with Answers

179 Physics MCQs that appeared in MDCAT 2024, arranged unit by unit in syllabus order. Tap “Show answer” under any question for the correct option and a short solution.

Force and Motion

1.The instantaneous velocity along the curved path is: (MDCAT 2024)

  1. along the tangent
  2. perpendicular to the slope
  3. parallel to the radius
  4. antiparallel to the radius
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Correct answer: (a) along the tangent

The instantaneous velocity is always directed along the tangent to the path at that point.

2.The instantaneous velocity along the curved path is ; (UHS MDCAT 2024)

  1. Along the tangent
  2. Perpendicular to the slope
  3. Parallel to the radius
  4. Anti-parallel to the radius
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Correct answer: (a) Along the tangent

The velocity at any instant points along the tangent to the path.

3.In a velocity-time graph the area under the graph is equal to the: (MDCAT 2024)

  1. speed of the object
  2. velocity of the object
  3. distance covered by the object
  4. acceleration of the object
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Correct answer: (c) distance covered by the object

The area is velocity multiplied by time, which is the distance covered.

4.In velocity time graph the area under graph is equal to the: (UHS MDCAT 2024)

  1. Speed of an object
  2. Velocity of an object
  3. Distance covered by object
  4. Acceleration of an object
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Correct answer: (c) Distance covered by object

Velocity times time is distance, and that is the area under the graph.

5.The two-dimensional motion under constant acceleration due to gravity is called: (MDCAT 2024)

  1. circular motion
  2. rotational motion
  3. projectile motion
  4. vibratory motion
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Correct answer: (c) projectile motion

A projectile moves in a vertical plane with the constant downward acceleration $g$.

6.126.The two dimensional motion under constant acceleration due to gravity is called: (UHS MDCAT 2024)

  1. Circular motion
  2. Rotational motion
  3. Projectile motion
  4. Vibratory motion
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Correct answer: (c) Projectile motion

Motion in two dimensions under gravity alone is projectile motion.

7.The vertical and horizontal component of the projectile motion are (KMU MDCAT 2024)

  1. Correlated with each other
  2. Dependent on each other
  3. Independent of each other
  4. Associated with each other
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Correct answer: (c) Independent of each other

Gravity acts only vertically, so the horizontal motion runs on unaffected.

8.A ball is kicked horizontally from the top of a 10m high cliff with an initial speed of 15m/s. After 2 seconds, which of the following statement describes the ball's horizontal and vertical components? (KMU MDCAT 2024)

  1. The horizontal velocity is 15m/s while vertical velocity is 20m/s downwards
  2. The horizontal velocity is 15m/s while vertical velocity is 15m/s downwards
  3. The horizontal velocity is 30m/s while vertical velocity is 20m/s downwards
  4. The horizontal velocity is 15m/s while vertical velocity is 0m/s
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Correct answer: (a) The horizontal velocity is 15m/s while vertical velocity is 20m/s downwards

The horizontal component stays at $15\,\mathrm{m\,s^{-1}}$, and the vertical one grows to $gt=20\,\mathrm{m\,s^{-1}}$.

9.The range of a projectile will be maximum if the factor $\sin2\theta$ becomes: (MDCAT 2024)

  1. zero
  2. 1
  3. $1/2$
  4. $-1$
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Correct answer: (b) 1

$R=v^2\sin2\theta/g$ is largest when $\sin2\theta=1$, that is at $\theta=45^\circ$.

10.The range of projectile will be maximum if the factor sin2θ becomes (UHS MDCAT 2024)

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

$R=v^2\sin2\theta/g$ is largest when the sine is one.

11.In projectile motion for which angle maximum height is half of its range? (NUMS MDCAT 2024)

  1. 73°
  2. 65°
  3. 63°
  4. 68°
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Correct answer: (c) 63°

$H=R/2$ gives $\tan\theta=2$, so the angle is about $63^{\circ}$.

12.Horizontal range of projectile will be maximum when: (NUMS MDCAT 2024)

  1. Sinθ = 1/2
  2. Sin2θ = 1
  3. Sinθ = 0
  4. Sin2θ = 0
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Correct answer: (b) Sin2θ = 1

$R=v^2\sin2\theta/g$ is largest when $\sin2\theta$ is one.

13.According to Newton's laws of motion the mass of an object is a quantitative measure of its: (MDCAT 2024)

  1. weight
  2. inertia
  3. speed
  4. acceleration
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Correct answer: (b) inertia

The greater the mass, the greater the force needed for a given acceleration, so mass measures inertia.

14.According to Newton's Law of Motion the mass of the object is a quantitative measure of its: (UHS MDCAT 2024)

  1. Weight
  2. Inertia
  3. Speed
  4. Acceleration
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Correct answer: (b) Inertia

Mass measures how strongly a body resists a change in its motion, that is its inertia.

15.____ is the natural tendency of an object to remain at rest or in motion with constant velocity? (KMU MDCAT 2024)

  1. Friction
  2. Inertia
  3. Mass
  4. Weight
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Correct answer: (b) Inertia

Inertia is the tendency of a body to keep its state of rest or of uniform motion.

16.If you stop your car quickly by wearing seat belts, chance of injury is greatly reduced because seat belt applied: (NUMS MDCAT 2024)

  1. Extra force
  2. Perpendicular force
  3. Opposite force
  4. Zero force
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Correct answer: (c) Opposite force

The belt supplies the backward force that stops the passenger, and it spreads that stop over a longer time.

17.A ball with momentum 8 kg m/s hits a wall and bounces back without losing K.E. Change in momentum is: (NUMS MDCAT 2024)

  1. 4 Ns
  2. -16 Ns
  3. 16 Ns
  4. 8 Ns
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Correct answer: (c) 16 Ns

The momentum goes from $+8$ to $-8$, a change of $16\,\mathrm{N\,s}$.

18.In an elastic collision the total kinetic energy: (MDCAT 2024)

  1. dissipates after the collision
  2. increases after the collision
  3. reduces after the collision
  4. before and after the collision remains the same
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Correct answer: (d) before and after the collision remains the same

An elastic collision is defined as one in which the kinetic energy is conserved.

19.In an elastic collision the total kinetic energy (UHS MDCAT 2024)

  1. Dissipates after collision
  2. Increases after the collision
  3. Reduces after the collision
  4. Before and after collision remains the same
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Correct answer: (d) Before and after collision remains the same

A collision is called elastic precisely because the kinetic energy is the same before and after.

20.A car in motion hits and gets crashed into a tree trunk, what is NOT conserved? (KMU MDCAT 2024)

  1. Kinetic energy alone
  2. Momentum alone
  3. Momentum and kinetic energy both
  4. Neither kinetic energy nor momentum
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Correct answer: (a) Kinetic energy alone

The crash is inelastic: momentum still holds, but kinetic energy goes into deformation and heat.

Work and Energy

21.Work done is equal to: (MDCAT 2024)

  1. effort $\times$ distance
  2. effort $+$ distance
  3. effort $-$ distance
  4. effort $\div$ distance
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Correct answer: (a) effort $\times$ distance

Work is the product of the force and the distance moved in the direction of the force.

22.When a force of 1 N displaces its point of application by 1 m in the direction of the force, the work done is: (MDCAT 2024)

  1. 1 J
  2. 10 J
  3. 0.1 J
  4. 100 J
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Correct answer: (a) 1 J

$W=Fd=1\times1=1$ J, which is how the joule is defined.

23.When a force of 1N displaces its point of application by 1m in the direction of force, the work done is (UHS MDCAT 2024)

  1. 1 J
  2. 10 J
  3. 0 J
  4. 1
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Correct answer: (a) 1 J

$W=Fd\cos0^{\circ}=1\times1$, which is one joule.

24.How does an angle between the force applied and the direction of motion influence the work done on an object? (KMU MDCAT 2024)

  1. Work is constant regardless of the angle
  2. Work is maximum when the angle is 0°
  3. Work is negative when the angle is 90°
  4. Work is 0 when the angle is 45°
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Correct answer: (b) Work is maximum when the angle is 0°

$W=Fd\cos\theta$ is greatest when the cosine is one, that is when force and displacement are along each other.

25.A nurse is pushing a wheelchair with an 80kg patient sitting on it. How much work is done by the patient's weight? (KMU MDCAT 2024)

  1. Half of the work
  2. Maximum work
  3. Minimum work
  4. No work
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Correct answer: (d) No work

The weight acts downwards and the chair moves horizontally, so the angle is $90^{\circ}$ and the work is nil.

26.If a constant force of 10N is applied to move an object 5m in the direction of the force, what is the work done? (KMU MDCAT 2024)

  1. 2 J
  2. 5 J
  3. 15 J
  4. 50 J
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Correct answer: (d) 50 J

$W=Fd=10\times5$, which is $50\,\mathrm{J}$.

27.At what angle of applied force, work done will be 50%? (NUMS MDCAT 2024)

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

$\cos\theta=0.5$ gives $\theta=60^{\circ}$.

28.The relation between K.E and momentum P is given by: (NUMS MDCAT 2024)

  1. K.E = 1/2 P/M
  2. K.E = 1/2 P/M2
  3. K.E = 1/2 P2/M2
  4. K.E = 1/2 P2/M
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Correct answer: (d) K.E = 1/2 P2/M

From $p=mv$, the kinetic energy $\tfrac12mv^2$ becomes $p^2/2m$.

29.The escape velocity of a body in the gravitational field of Earth is dependent on: (KMU MDCAT 2024)

  1. Angle on which it is thrown
  2. Both mass of the body and the angle at which it is thrown
  3. Mass of earth
  4. Mass of the body
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Correct answer: (c) Mass of earth

Escape velocity is $\sqrt{2GM/R}$, which carries the mass of the Earth but not that of the body.

30.When dolphin leaves the water it has lots of kinetic energy. At its highest point its energy is: (NUMS MDCAT 2024)

  1. Kinetic energy
  2. Potential energy
  3. Elastic potential energy
  4. Neither kinetic nor potential energy
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Correct answer: (b) Potential energy

At the top the motion has stopped rising and all the energy is potential.

31.The absolute potential energy is given as Ug = -GmMe/R. The negative sign indicates Earth's gravitational field for mass 'm' is: (NUMS MDCAT 2024)

  1. Repulsive
  2. Less attractive
  3. Attractive
  4. More repulsive less attractive
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Correct answer: (c) Attractive

Work must be done against the field to carry the mass away, so the bound state is negative.

32.One kilowatt-hour is equal to: (MDCAT 2024)

  1. 3.6 J
  2. 3.6 kJ
  3. 3.6 MJ
  4. 36 MJ
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Correct answer: (c) 3.6 MJ

$1\ \mathrm{kWh}=1000\times3600=3.6\times10^{6}$ J, which is 3.6 MJ.

33.An electric motor is used to lift a weight of 2.0 N through a vertical distance of 100 cm in 4 s. What is the power output of the motor? (MDCAT 2024)

  1. 0.25 W
  2. 0.5 W
  3. 0.75 W
  4. 1 W
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Correct answer: (b) 0.5 W

$P=W/t=(2.0\times1.0)/4=0.5$ W.

34.An electric motor is used to lift the weight of 2.0N through a vertical distance of 100 cm in 4 sec. What is the power output of the motor? (UHS MDCAT 2024)

  1. 0.25 W
  2. 0.5 W
  3. 0.75 W
  4. 1 W
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Correct answer: (b) 0.5 W

$P=W/t=2\times1/4$, which is $0.5\,\mathrm{W}$.

35.Which of the following pairs correctly matches a physical quantity with its SI unit? (KMU MDCAT 2024)

  1. Energy- Newton
  2. Force- Joule
  3. Power- Watt
  4. Velocity-m/s^2
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Correct answer: (c) Power- Watt

Power is measured in watts; force in newtons and energy in joules.

36.What is the power of electric motor when it performs work of 64 × 106 J in 8 seconds? (NUMS MDCAT 2024)

  1. 6 Kilowatts
  2. 7 Kilowatts
  3. 8 Megawatts
  4. 7 Megawatts
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Correct answer: (c) 8 Megawatts

$P=W/t=64\times10^6/8$, which is $8\,\mathrm{MW}$.

37.Which of the following is a non-conservative force? (MDCAT 2024)

  1. frictional force
  2. electric force
  3. elastic spring force
  4. gravitational force
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Correct answer: (a) frictional force

The work done against friction depends on the path taken and is not recovered, so friction is non-conservative.

Rotational and Circular Motion

38.A wheel makes 3 complete revolutions. What is the total number of radians through which a point on wheel has rotated? (KMU MDCAT 2024)

  1. 2π
  2. 3π
  3. 6π
  4. 9π
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Correct answer: (c) 6π

Each revolution is $2\pi$ radians, so three of them are $6\pi$.

39.For rigid body that rotates about a fixed axis, the angle swept out by a line passing through any point on the body and intersecting the axis of rotation perpendicularly is called? (KMU MDCAT 2024)

  1. Angular acceleration
  2. Angular displacement
  3. Angular momentum
  4. Angular velocity
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Correct answer: (b) Angular displacement

That angle is the angular displacement of the body.

40.Sara goes around a circular track of diameter 20m for distance 180m. Angular displacement is: (NUMS MDCAT 2024)

  1. 16 radians
  2. 18 radians
  3. 50 radians
  4. 8 radians
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Correct answer: (b) 18 radians

$\theta=s/r=180/10$, which is $18$ radians.

41.To find the direction of angular displacement, use: (NUMS MDCAT 2024)

  1. Grasp axis of rotation in right hand
  2. Grasp axis of rotation in left hand
  3. Put thumb of right hand in direction of circular motion
  4. Put thumb of left hand in direction of circular motion
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Correct answer: (a) Grasp axis of rotation in right hand

Grasp the axis in the right hand with the fingers along the turn, and the thumb gives the direction.

42.For anti-clockwise rotation the angular displacement is: (NUMS MDCAT 2024)

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

An anticlockwise rotation is taken as positive, with its vector out of the page.

43.How many degrees in 2π/5 radians? (NUMS MDCAT 2024)

  1. 80°
  2. 50°
  3. 72°
  4. 20°
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Correct answer: (c) 72°

$\pi$ radians is $180^{\circ}$, so $2\pi/5$ is $72^{\circ}$.

44.An aircraft makes a turn in a horizontal circle of radius 100 m. It is travelling with a velocity of $250\ \mathrm{m\,s^{-1}}$. The angular velocity of the aircraft will be: (MDCAT 2024)

  1. $1.5\ \mathrm{rad\,s^{-1}}$
  2. $2.5\ \mathrm{rad\,s^{-1}}$
  3. $3\ \mathrm{rad\,s^{-1}}$
  4. $3.5\ \mathrm{rad\,s^{-1}}$
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Correct answer: (b) $2.5\ \mathrm{rad\,s^{-1}}$

$\omega=v/r=250/100=2.5\ \mathrm{rad\,s^{-1}}$.

45.An air craft makes a turn in a horizontal circle of radius100m. It is travelling with a velocity of 250m/sec. The angular velocity of the air craft will be: (UHS MDCAT 2024)

  1. 1.5 rad/sec
  2. 2.5 rad/sec
  3. 3 rad/sec
  4. 3.5 rad/sec
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Correct answer: (b) 2.5 rad/sec

$\omega=v/r=250/100$, which is $2.5\,\mathrm{rad\,s^{-1}}$.

46.The velocity of an object moving in a circle is: (NUMS MDCAT 2024)

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

The direction changes at every point, so the velocity is not constant even at constant speed.

47.Angle swept by minute hand in one minute is: (NUMS MDCAT 2024)

  1. 6°
  2. 36°
  3. 8°
  4. 20°
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Correct answer: (a) 6°

The hand sweeps $360^{\circ}$ in sixty minutes, so $6^{\circ}$ in one.

48.A particle moves in a circle of radius 10m with speed 20 m/s. Find angular velocity: (NUMS MDCAT 2024)

  1. 2 rad/s
  2. 200 rad/s
  3. 20 rad/s
  4. 10 rad/s
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Correct answer: (a) 2 rad/s

$\omega=v/r=20/10$, which is $2\,\mathrm{rad\,s^{-1}}$.

49.The centripetal acceleration of an object moving along a circle of radius $r$ with an angular speed $\omega$ is given by the formula: (MDCAT 2024)

  1. $a=r\omega^2$
  2. $a=r\omega$
  3. $a=\omega^2/r$
  4. $a=r/\omega^2$
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Correct answer: (a) $a=r\omega^2$

With $v=r\omega$, $a=v^2/r=r^2\omega^2/r=r\omega^2$.

50.A particle of mass $m$ moving on a circular path of radius $r$ with velocity $v$ has a centripetal force $F$ acting on it. If the velocity increases 2 times and the radius increases 4 times, the new centripetal force is: (MDCAT 2024)

  1. $2F$
  2. $F/2$
  3. $4F$
  4. $F$
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Correct answer: (d) $F$

$F=mv^2/r$, and $m(2v)^2/(4r)=4mv^2/(4r)=F$.

51.A roller coaster is moving with $30\ \mathrm{m\,s^{-1}}$ on a circular track of radius 30 m. If the net mass of coaster and passengers is $m$, the centripetal force acting on it is: (MDCAT 2024)

  1. $900m$
  2. $9m$
  3. $450m$
  4. $30m$
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Correct answer: (d) $30m$

$F=mv^2/r=m(30)^2/30=30m$.

52.The centripetal acceleration of an object moving along a circle of radius 'r' with an angular speed 'w' is given by the formula: (UHS MDCAT 2024)

  1. a = rw^2
  2. a = r ω
  3. a = r^2 ω
  4. A = r^2 ω^2
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Correct answer: (a) a = rw^2

With $v=r\omega$, the centripetal acceleration $v^2/r$ becomes $r\omega^2$.

53.A particle of mass 'm' is moving on a circular path of radius 'r' with velocity 'v', then centripetal force acting on it is F. If the velocity of particle increases by 2 times and radius of circular path increases by 4 times then new centripetal force F' will be; (UHS MDCAT 2024)

  1. F' = 2 F
  2. F' = 1/2 F
  3. F' = 4 F
  4. F' = F
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Correct answer: (d) F' = F

$F=mv^2/r$ gains a factor of four from the speed and loses four to the radius, so it is unchanged.

54.A roller coaster is moving with 30 ms-1 on a circular track of radius 30m. the net mass of coaster + passengers is 'm' the centripetal force acting on it is: (UHS MDCAT 2024)

  1. 900m
  2. m
  3. 450 m
  4. 30m
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Correct answer: (d) 30m

$F=mv^2/r=m\times900/30$, which is $30m$.

55.A car is moving in a circular path at a constant speed. What provides the necessary centripetal force to keep the car moving in this path? (KMU MDCAT 2024)

  1. The car's inertia resisting any change in direction
  2. The car's mass pulling it towards the centre of the circle
  3. The engine's power pushing the car forward
  4. The friction between the tyres and the road
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Correct answer: (d) The friction between the tyres and the road

The friction of the tyres on the road is the only inward force there is.

56.In a rotating spaceship, to produce artificial gravity, what does the centripetal force do? (KMU MDCAT 2024)

  1. Has no effect inside the spaceship
  2. Increases spaceship's rotation
  3. Pulls objects towards the centre
  4. Pushes the objects towards the outer wall
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Correct answer: (d) Pushes the objects towards the outer wall

The wall must push the occupant inwards, and by the third law they press outwards on it, which feels like weight.

57.When the mass of a body moving along a circle becomes half and radius becomes double, and v is constant, the centripetal force becomes? (KMU MDCAT 2024)

  1. Double
  2. Half
  3. One-fourth
  4. Remains Same
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Correct answer: (c) One-fourth

$F=mv^2/r$ loses a half to the mass and another half to the radius, so a quarter is left.

Waves

58.In transverse waves the portion above the mean level is called the: (MDCAT 2024)

  1. wave front
  2. wave crest
  3. wave trough
  4. wavelength
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Correct answer: (b) wave crest

The high point of a transverse wave is a crest; the low point is a trough.

59.The distance between two successive particles which are exactly in the same state of vibration is called: (MDCAT 2024)

  1. frequency
  2. amplitude
  3. wavelength
  4. time period
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Correct answer: (c) wavelength

Particles one wavelength apart are in phase, which is what the same state of vibration means.

60.In transverse waves the portion above the mean level is called: (UHS MDCAT 2024)

  1. Wave front
  2. Wave crest
  3. Wave trough
  4. Wave length
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Correct answer: (b) Wave crest

The rise above the undisturbed level is a crest; the dip below it is a trough.

61.The distance between two successive particles which are exactly in the same state of vibration is called (UHS MDCAT 2024)

  1. Frequency
  2. Amplitude
  3. Wavelength
  4. Time period
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Correct answer: (c) Wavelength

The distance between two particles in the same phase is one wavelength.

62.Normal person hears 20Hz to 20KHz. Maximum wavelength is: (NUMS MDCAT 2024)

  1. 17m
  2. 17mm
  3. 17cm
  4. 17km
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Correct answer: (a) 17m

The longest wavelength goes with the lowest frequency, $340/20$, that is about $17\,\mathrm{m}$.

63.Which type of waves can be polarized? (KMU MDCAT 2024)

  1. Longitudinal waves
  2. Mechanical waves
  3. Sound waves
  4. Transverse waves
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Correct answer: (d) Transverse waves

Only a transverse wave has a vibration direction to single out, so only it can be polarized.

64.For longitudinal waves (KMU MDCAT 2024)

  1. The particles of the medium oscillate perpendicular to the wave's propagation
  2. The particles of the medium remain stationary as the wave passes through
  3. The particles of the medium oscillate along the direction of the wave's propagation
  4. Their velocity is enhanced when they travel through vacuum
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Correct answer: (c) The particles of the medium oscillate along the direction of the wave's propagation

In a longitudinal wave the particles move to and fro along the line the wave travels.

65.Speed of sound in solid is greater than in air because ratio: (NUMS MDCAT 2024)

  1. (√E/ρ) solid < (√E/ρ) air
  2. (√E/ρ) solid > (√E/ρ) air
  3. (√E/ρ) solid = (√E/ρ) air
  4. (√E/ρ) solid ≤ (√E/ρ) air
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Correct answer: (b) (√E/ρ) solid > (√E/ρ) air

$v=\sqrt{E/\rho}$, and a solid gains far more in elasticity than it loses to density.

66.What happens when two waves of the same frequency and amplitude meet in phase? (KMU MDCAT 2024)

  1. They cancel each other out resulting in a destructive interference
  2. They combine to form a wave double the amplitude, resulting in constructive interference
  3. They produce a wave with zero amplitude
  4. They produce a wave with the same amplitude as the individual waves
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Correct answer: (b) They combine to form a wave double the amplitude, resulting in constructive interference

Crest falls on crest, and the displacements add to give twice the amplitude.

67.According to the principle of superimposition, when 2 or more waves overlap at a point in space, the amplitude of the resultant wave at that point is (KMU MDCAT 2024)

  1. Always zero
  2. The product of the individual wave amplitude
  3. The product of the frequencies of the individual waves
  4. The sum of the amplitudes of the individual waves
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Correct answer: (d) The sum of the amplitudes of the individual waves

The resultant displacement at any point is the sum of the separate displacements there.

68.Which one of the following is INCORRECT about the nodes when a string is plucked? (MDCAT 2024)

  1. the amplitude of vibration is zero
  2. they do not move along the string
  3. they are produced at the fixed ends of the string
  4. the distance between consecutive nodes is one wavelength
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Correct answer: (d) the distance between consecutive nodes is one wavelength

Consecutive nodes are half a wavelength apart, not a whole wavelength.

69.Which one of the following does not cause stationary waves? (MDCAT 2024)

  1. two waves of equal frequency
  2. two waves of the same speed
  3. two waves of unequal amplitude
  4. two waves travelling in opposite directions
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Correct answer: (c) two waves of unequal amplitude

Stationary waves need two waves of equal amplitude; unequal amplitudes leave a travelling wave over the pattern.

70.Which one of the following does not cause stationary waves? (UHS MDCAT 2024)

  1. Two waves of equal frequency
  2. Two waves of same speed
  3. Two waves of unequal amplitude
  4. Two waves travelling in opposite directions
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Correct answer: (c) Two waves of unequal amplitude

Two waves need equal amplitude for the nodes to be true zeros; everything else here is required.

71.Which one of the following is INCORRECT about the nodes when the string is plucked; (UHS MDCAT 2024)

  1. Amplitude of vibration is zero
  2. Do not move along the string
  3. Produced at the fixed ends of strings
  4. Distance between consecutive nodes is 1 wavelength
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Correct answer: (d) Distance between consecutive nodes is 1 wavelength

Consecutive nodes are half a wavelength apart, not a whole one.

72.Body mass 10kg, spring k=20 N/m, max displacement 20cm. Acceleration is: (NUMS MDCAT 2024)

  1. 2.2 ms−2
  2. 4 ms−2
  3. 2 ms−2
  4. 0.4 ms−2
Show answer

Correct answer: (d) 0.4 ms−2

$a=kx/m=20\times0.2/10$, which is $0.4\,\mathrm{m\,s^{-2}}$.

Thermodynamics

73.Consider an ideal gas confined to the cylinder with a fixed piston, on heating the gas, all the heat supplied increases (KMU MDCAT 2024)

  1. Kinetic energy of the molecules
  2. Potential Energy of the molecules
  3. The intermolecular forces between gas molecules
  4. The number of gas molecules
Show answer

Correct answer: (a) Kinetic energy of the molecules

An ideal gas has no intermolecular forces, so all the heat goes into the motion of its molecules.

74.During the isothermal process, the temperature (UHS MDCAT 2024)

  1. remains constant during the initial phase of the process of the process
  2. remains constant throughout the process
  3. alters throughout the process
  4. increases throughout the process
Show answer

Correct answer: (b) remains constant throughout the process

Isothermal means at one temperature, held so throughout the change.

75.In an adiabatic process, how does the temperature of a gas change as its volume decreases? (KMU MDCAT 2024)

  1. The temperature decreases
  2. The temperature increases
  3. The temperature remains constant
  4. The temperature first increases then decreases
Show answer

Correct answer: (b) The temperature increases

No heat can escape, so the work done in compressing the gas all goes into its internal energy.

76.During an isothermal expansion of an ideal gas, which of the following statement is true? (KMU MDCAT 2024)

  1. Pressure and temperature of the gas increase
  2. The internal energy of the gas increases
  3. The temperature of the gas remains constant
  4. The work done by the gas is zero
Show answer

Correct answer: (c) The temperature of the gas remains constant

Isothermal means at constant temperature, held so by heat flowing in as the gas does work.

77.During an isothermal process the temperature: (MDCAT 2024)

  1. remains constant during the initial phases of the process
  2. remains constant throughout the process
  3. alters throughout the process
  4. increases throughout the process
Show answer

Correct answer: (b) remains constant throughout the process

Isothermal means at one temperature, so the temperature is constant for the whole process.

78.What is the value of the heat energy $Q$ in an adiabatic process? (MDCAT 2024)

  1. $-1$
  2. $+1$
  3. 0
  4. $+2$
Show answer

Correct answer: (c) 0

No heat enters or leaves the system in an adiabatic process, so $Q=0$ and the work is done at the cost of internal energy.

79.What is the value of heat energy (Q) in an adiabatic process? (UHS MDCAT 2024)

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

Correct answer: (c) 0

An adiabatic change is one in which no heat enters or leaves, so $Q$ is zero.

80.A process in which all heat energy is used for increasing internal energy is: (NUMS MDCAT 2024)

  1. Isobaric
  2. Isochoric
  3. Isothermal
  4. Adiabatic
Show answer

Correct answer: (b) Isochoric

At constant volume no work is done, so by the first law all the heat goes into internal energy.

Electrostatics

81.Coulomb's law states that the force between two point charges is: (MDCAT 2024)

  1. inversely proportional to the product of the charges and directly proportional to the square of the distance between them
  2. directly proportional to the product of the charges and inversely proportional to the square of the distance between them
  3. directly proportional to the sum of the charges and inversely proportional to the square of the distance between them
  4. directly proportional to the product of the charges and to the square of the distance between them
Show answer

Correct answer: (b) directly proportional to the product of the charges and inversely proportional to the square of the distance between them

$F=q_1q_2/4\pi\varepsilon_0r^2$.

82.The Coulomb's law states (UHS MDCAT 2024)

  1. Force,between two point charges is inversely proportional to the product of the charges and directly proportional to the square of the distance between them
  2. Force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them
  3. Force between two point charges is directly proportional to the sum of the charges and inversely proportional to the square of the distance between them
  4. Force between two point charges is directly proportional to the product of the charges and the square of the distance between them
Show answer

Correct answer: (b) Force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them

$F=kq_1q_2/r^2$: proportional to the product of the charges and to the inverse square of the separation.

83.151.Which one of the following Is NOT a feature of electric forces? (UHS MDCAT 2024)

  1. They act on charges
  2. They act on masses
  3. They can be attractive
  4. They can be repulsive
Show answer

Correct answer: (b) They act on masses

Electric forces act on charge; it is gravitation that acts on mass.

84.What is the increase in force between two charges if the separation between them is decreased by 50 percent? (KMU MDCAT 2024)

  1. Becomes four times
  2. Doubles
  3. Increases by half
  4. Triples
Show answer

Correct answer: (a) Becomes four times

Halving the separation multiplies the inverse square by four.

85.According to Coulomb's law, what happens to the electrostatic force between the 2-point charges if the distance between them is doubled? (KMU MDCAT 2024)

  1. The force becomes one-fourth
  2. The force becomes half
  3. The force doubles
  4. The force remains the same
Show answer

Correct answer: (a) The force becomes one-fourth

Doubling the separation leaves a quarter of the force.

86.NaCl dissolves quickly in water due to: (NUMS MDCAT 2024)

  1. Low εr
  2. High εr
  3. εr = 0
  4. εr = ∞
Show answer

Correct answer: (b) High εr

Water has a very high relative permittivity, so it weakens the attraction between the ions to about a eightieth.

87.Which one of the following is NOT a feature of electric forces? (MDCAT 2024)

  1. they act on charges
  2. they act on masses
  3. they can be attractive
  4. they can be repulsive
Show answer

Correct answer: (b) they act on masses

Electric forces act on charge; it is the gravitational force that acts on mass.

88.The electric intensity between two oppositely charged plates in the middle region is: (MDCAT 2024)

  1. non-uniform
  2. uniform
  3. unpredictable
  4. variable
Show answer

Correct answer: (b) uniform

Away from the edges the field between two parallel charged plates is uniform, $E=\sigma/\varepsilon_0$.

89.149.Electric intensity between two oppositely charge plates in the middle region is_______ (UHS MDCAT 2024)

  1. Non-uniform
  2. Uniform
  3. Cannot be predicted
  4. Variable
Show answer

Correct answer: (b) Uniform

Between two large parallel plates the field lines are straight and evenly spaced, so the field is uniform.

90.The formula $V=W/q$ represents: (MDCAT 2024)

  1. electric intensity
  2. electric power
  3. electric potential
  4. electric field gradient
Show answer

Correct answer: (c) electric potential

Potential is the work done per unit positive charge in bringing it from infinity to that point.

91.Find the potential difference in moving a 2 C charge which requires 600 J of work between two points. (MDCAT 2024)

  1. 1200 V
  2. 300 V
  3. 150 V
  4. 2400 V
Show answer

Correct answer: (b) 300 V

$V=W/q=600/2=300$ V.

92.The formula V = W / qo represents (UHS MDCAT 2024)

  1. Electric intensity
  2. Electric power
  3. Electric potential
  4. Electric field gradient
Show answer

Correct answer: (c) Electric potential

Work per unit charge is the electric potential.

93.150.Find potential difference in moving 2 C charge which requires 600J of work between two points. (UHS MDCAT 2024)

  1. 1200V
  2. 300V
  3. 150V
  4. 2400V
Show answer

Correct answer: (b) 300V

$V=W/q=600/2$, which is $300\,\mathrm{V}$.

94.Electron Volt (eV) is another unit of (KMU MDCAT 2024)

  1. Charge
  2. Current
  3. Energy
  4. Power
Show answer

Correct answer: (c) Energy

An electron volt is the energy an electron gains through a potential difference of one volt.

95.A particle with charge 1C moves through potential difference 5V. Energy required: (NUMS MDCAT 2024)

  1. 5×10−10 J
  2. 8×10−18 J
  3. 8J
  4. 5J
Show answer

Correct answer: (d) 5J

$W=qV=1\times5$, which is $5\,\mathrm{J}$.

96.Two points charges, +5µC and -5µC are placed at points A and B, respectively, which are separated by a distance 2d. What is the electric potential at the midpoint M of the line joining A and B? (KMU MDCAT 2024)

  1. 2kQ/d
  2. kQ/d
  3. -kQ/d
  4. zero
Show answer

Correct answer: (d) zero

Potential is a scalar, and the two equal and opposite contributions cancel at the midpoint.

97.At midpoint P between two +4μc charges. V and E at midpoint P: (NUMS MDCAT 2024)

  1. V=0, E≠0
  2. V=0, E=0
  3. V≠0, E≠0
  4. V≠0, E=0
Show answer

Correct answer: (d) V≠0, E=0

The two potentials add and the two fields cancel, so the potential is finite and the field is zero.

98.The SI unit of the capacitance of a capacitor is the: (MDCAT 2024)

  1. coulomb
  2. volt
  3. farad
  4. ampere
Show answer

Correct answer: (c) farad

One farad is one coulomb per volt.

99.The S.I unit of capacitance of a capacitor is: (UHS MDCAT 2024)

  1. Coulomb
  2. Volt
  3. Farad
  4. Ampere
Show answer

Correct answer: (c) Farad

Capacitance is measured in farads, one farad being a coulomb per volt.

100.In the case of a parallel plate capacitor, when the distance between the two plates is reduced to half and the area of the plate doubled, the capacitance (KMU MDCAT 2024)

  1. Increases four times
  2. Increases six times
  3. Is doubled
  4. Remains the same
Show answer

Correct answer: (a) Increases four times

$C=\varepsilon A/d$ gains two from the area and two from the halved separation.

101.If the dielectric material between the plates of the capacitor is removed, what happens to the electric field between the plates? (KMU MDCAT 2024)

  1. The electric field becomes zero
  2. The electric field decreases
  3. The electric field increases
  4. The electric field remains the same
Show answer

Correct answer: (c) The electric field increases

The dielectric was weakening the field; with the charge unchanged, taking it out lets the field rise.

102.Capacitance of a capacitor increases with a decrease in: (KMU MDCAT 2024)

  1. Dielectric constant
  2. Plate area
  3. Permittivity
  4. Plate separation
Show answer

Correct answer: (d) Plate separation

$C=\varepsilon A/d$, so the closer the plates the greater the capacitance.

103.A capacitor can be fully charged because time required is: (NUMS MDCAT 2024)

  1. 1 time constant
  2. 2 time constant
  3. 4 time constant
  4. Infinity
Show answer

Correct answer: (d) Infinity

The charge approaches its final value asymptotically, so strictly it is never quite reached.

104.If electric field intensity between capacitor plates doubles, energy stored becomes: (NUMS MDCAT 2024)

  1. Double
  2. One half
  3. One Fourth
  4. Quadruple
Show answer

Correct answer: (d) Quadruple

The energy density goes as the square of the field, so doubling the field gives four times the energy.

Current Electricity

105.A charge of 90 C passes through a wire for 30 seconds. The current in the wire will be: (MDCAT 2024)

  1. 3 A
  2. 0.3 A
  3. 3 mA
  4. 0.3 mA
Show answer

Correct answer: (a) 3 A

$I=q/t=90/30=3$ A.

106.152.A charge of 90 C passes through a wire for 30 seconds. Then the current in the wire will be: (UHS MDCAT 2024)

  1. 3A
  2. 0.3 A
  3. 3 mA
  4. 0.3 mA
Show answer

Correct answer: (a) 3A

$I=q/t=90/30$, which is $3\,\mathrm{A}$.

107.What does one Coulomb represent in terms of charge? (KMU MDCAT 2024)

  1. The amount of charge transported by a current of one Ampere in one second
  2. The charge of one proton
  3. The charge of one electron
  4. The charge required to create a force of 1 Newton between two charges separated by 1meter
Show answer

Correct answer: (a) The amount of charge transported by a current of one Ampere in one second

One coulomb is the charge carried past a point by one ampere in one second.

108.The statement that the magnitude of the current in a metal is proportional to the potential difference across it as long as the temperature of the conductor is kept constant is known as: (MDCAT 2024)

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

Correct answer: (c) Ohm's law

That proportionality at constant temperature is Ohm's law, $V=IR$.

109.153.The magnitude of the current in metals is proportional to the potential difference across it as long as temperature of conductor is kept constant is known as: (UHS MDCAT 2024)

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

Correct answer: (c) Ohm's Law

That is Ohm’s law.

110.156.Volt x Ampere is the measure of; (UHS MDCAT 2024)

  1. Current
  2. Volt
  3. Resistance
  4. Power
Show answer

Correct answer: (d) Power

Volts times amperes is watts, the unit of power.

111.The I-V Graph for a non-Ohmic material is always (KMU MDCAT 2024)

  1. Curved
  2. Horizontal
  3. Linear
  4. Perpendicular
Show answer

Correct answer: (a) Curved

A non-ohmic conductor has no constant resistance, so its current voltage graph is not a straight line.

112.If R1 and R2 are respectively the filament resistance of a 100-Watt bulb and 200-Watt bulb designed to operate on the same voltage, then power of: (KMU MDCAT 2024)

  1. R1 is two times R2
  2. R2 is two times R1
  3. R2 is four times R1
  4. R1 is four times R2
Show answer

Correct answer: (a) R1 is two times R2

$R=V^2/P$ at the same voltage, so the $100\,\mathrm{W}$ filament has twice the resistance of the $200\,\mathrm{W}$ one.

113.Equivalent resistance between A and B (three 1Ω resistors in parallel): (NUMS MDCAT 2024)

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

Correct answer: (b) 1/3 Ω

Three equal resistors in parallel give a third of one of them.

114.When the length of a copper wire is doubled, its resistivity becomes: (MDCAT 2024)

  1. double
  2. half
  3. the same
  4. four times
Show answer

Correct answer: (c) the same

Resistivity is a property of the material and not of the length; it is the resistance that doubles.

115.The resistance of a semiconductor with a rise in temperature: (MDCAT 2024)

  1. increases
  2. decreases
  3. remains the same
  4. becomes infinite
Show answer

Correct answer: (b) decreases

Heating a semiconductor frees many more charge carriers, so its resistance falls.

116.154.When length of copper wire is doubled then resistivity becomes: (UHS MDCAT 2024)

  1. Double
  2. Half
  3. Remains same
  4. Four times
Show answer

Correct answer: (c) Remains same

Resistivity is a property of the material, so stretching the wire does not change it.

117.155.The resistance of semi-conductor with rise in temperature (UHS MDCAT 2024)

  1. Increases
  2. Decreases
  3. Remain same
  4. Infinite
Show answer

Correct answer: (b) Decreases

Heating a semiconductor frees more carriers, so its resistance falls.

118.Temperature coefficient of resistance is defined as increase in resistance per ohm original resistance per ___? (KMU MDCAT 2024)

  1. Degree rise in temperature
  2. Unit increase in electric current
  3. Unit decrease in capacitance
  4. Degree drop in temperature
Show answer

Correct answer: (a) Degree rise in temperature

It is the fractional rise in resistance for each degree of temperature.

119.For metals, the temperature coefficient of resistance is: (KMU MDCAT 2024)

  1. Infinity
  2. Negative
  3. Positive
  4. Zero
Show answer

Correct answer: (c) Positive

A metal grows more resistive as it is heated, so its coefficient is positive.

120.The substance having negative temperature coefficient of resistance is: (NUMS MDCAT 2024)

  1. Insulators
  2. Conductor
  3. Semi-conductor
  4. Alloys
Show answer

Correct answer: (c) Semi-conductor

Heating a semiconductor frees carriers, so its resistance falls and its coefficient is negative.

121.Volt $\times$ ampere is the measure of: (MDCAT 2024)

  1. current
  2. potential difference
  3. resistance
  4. power
Show answer

Correct answer: (d) power

$P=VI$, so a volt-ampere is a watt.

122.The maximum power transfer theorem states that maximum power is delivered to the load when (KMU MDCAT 2024)

  1. The load resistance is half of the source resistance
  2. The load resistance is zero
  3. The load resistance is double the source resistance
  4. The load resistance is equal to the source resistance
Show answer

Correct answer: (d) The load resistance is equal to the source resistance

Most power reaches the load when its resistance matches the internal resistance of the source.

Electromagnetism

123.Which of the following statements is incorrect for magnetic field lines? (MDCAT 2024)

  1. lines start at the north pole and end at the south pole
  2. lines never touch or cross each other
  3. the lines are curved
  4. the magnetic field is strongest where the lines are farthest apart
Show answer

Correct answer: (d) the magnetic field is strongest where the lines are farthest apart

The field is strongest where the lines are closest together, not farthest apart.

124.The unit of magnetic flux density is: (MDCAT 2024)

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

Correct answer: (c) $\mathrm{Wb\,m^{-2}}$

Flux density is flux per unit area, and $1\ \mathrm{Wb\,m^{-2}}=1$ T.

125.158.Which of the following statement is incorrect for any magnetic field lines? (UHS MDCAT 2024)

  1. Lines start at north pole and ends at south pole
  2. Lines never touch or cross each other
  3. The lines are curved
  4. Magnetic field is strongest when the lines are farthest
Show answer

Correct answer: (d) Magnetic field is strongest when the lines are farthest

The field is strongest where the lines are crowded together, not where they are far apart.

126.159.The unit of magnetic flux density is ; (UHS MDCAT 2024)

  1. Wbm-1
  2. Wbm
  3. Wbm-2
  4. Wb
Show answer

Correct answer: (c) Wbm-2

Flux density is flux per unit area, that is webers per square metre, or tesla.

127.Which of the following statement is true about the magnetic filed inside a solenoid? (KMU MDCAT 2024)

  1. It is along the axis of the coil
  2. It is circular around the wires
  3. It is strongest at the ends of the solenoid
  4. It is zero when current flows through it
Show answer

Correct answer: (a) It is along the axis of the coil

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

128.The formula $\Phi=\vec{B}\cdot\vec{A}$ represents: (MDCAT 2024)

  1. electric flux
  2. magnetic flux
  3. electric flux density
  4. gravitational flux
Show answer

Correct answer: (b) magnetic flux

Magnetic flux is the scalar product of the magnetic field and the area it threads.

129.157.The formula Φ = B.A represents (UHS MDCAT 2024)

  1. Electric flux
  2. Magnetic flux
  3. Electric flux density
  4. Gravitational flux
Show answer

Correct answer: (b) Magnetic flux

Flux density times area, taken as a scalar product, is the magnetic flux.

130.An electron is moving perpendicular to the magnetic field, which of the following is correct statement about electromagnetic force acting on the electron? (KMU MDCAT 2024)

  1. Force acting is equal to electron charge
  2. Force acting is equal to the magnetic field strength
  3. Force acting is maximum
  4. Zero force is acting on it
Show answer

Correct answer: (c) Force acting is maximum

$F=qvB\sin\theta$ is greatest when the angle is a right angle.

131.For a positive charged particle (q) moving with a velocity (v) in a magnetic Filed of flux density B, the force (F) acting on the charge particle is given by the expression? (KMU MDCAT 2024)

  1. F = Fv x B
  2. F = qv x B
  3. F = v x B/q
  4. q = v x B/F
Show answer

Correct answer: (b) F = qv x B

The magnetic force on a moving charge is the vector product $q\mathbf{v}\times\mathbf{B}$.

Electromagnetic Induction

132.In an AC generator the emf will be maximum when the factor $\sin\omega t$ is equal to: (MDCAT 2024)

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

Correct answer: (b) 1

$\varepsilon=\varepsilon_0\sin\omega t$ is greatest when $\sin\omega t=1$.

133.Electric generators and transformers are based on the principle of: (MDCAT 2024)

  1. Coulomb's law
  2. Faraday's law
  3. Ampere's law
  4. Hooke's law
Show answer

Correct answer: (b) Faraday's law

Both work by inducing an emf with a changing magnetic flux, which is Faraday's law.

134.161.In an AC generator the emf will be maximum when factor sinωt is equal to (UHS MDCAT 2024)

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

Correct answer: (b) 1

The emf is $\varepsilon_0\sin\omega t$, largest when the sine reaches one.

135.162.Electric generators and transformers are based on the principles of: (UHS MDCAT 2024)

  1. Coulomb's law
  2. Faraday's law
  3. Ampere's law
  4. Hook's law
Show answer

Correct answer: (b) Faraday's law

Both work by inducing an emf with a changing flux, which is Faraday’s law.

136.One-meter-long copper rod is moving with speed 20 m/sec in the magnetic field of strength 0.6 tesla what is the value of induced emf? (KMU MDCAT 2024)

  1. 12 V
  2. 19.4 V
  3. 20.6 V
  4. 25 V
Show answer

Correct answer: (a) 12 V

$\varepsilon=BLv=0.6\times1\times20$, which is $12\,\mathrm{V}$.

137.The inductance of a coil depends on. (KMU MDCAT 2024)

  1. Number of turns
  2. Resistance of the wire used
  3. Type of insulation used on the wire
  4. Voltage applied to the coil
Show answer

Correct answer: (a) Number of turns

Inductance goes as the square of the number of turns, with the area, the length and the core.

138.The statement that the induced current will flow in such a direction as to oppose the cause that produces it is: (MDCAT 2024)

  1. Ampere's law
  2. Faraday's law
  3. Lenz's law
  4. Joule's law
Show answer

Correct answer: (c) Lenz's law

That is Lenz's law, and it is the conservation of energy applied to induction.

139.160.The induced current will flow in such a direction so as to oppose the cause that produces it is statement of: (UHS MDCAT 2024)

  1. Ampere's Law
  2. Faraday's Law
  3. Lenz's Law
  4. Joule's Law
Show answer

Correct answer: (c) Lenz's Law

That is Lenz’s law.

140.The direction of induced current is determined by? (KMU MDCAT 2024)

  1. Ampere’s law
  2. Faraday’s law
  3. Lenz’s law
  4. Ohm’s law
Show answer

Correct answer: (c) Lenz’s law

Lenz’s law fixes the direction; Faraday’s law gives the size.

141.Lenz’s law is consistent with the (KMU MDCAT 2024)

  1. Ampere’s Law
  2. Faraday’s law
  3. Law of conservation of energy
  4. Ohm’s law
Show answer

Correct answer: (c) Law of conservation of energy

If the induced current helped the change, energy would be made from nothing.

142.In an ideal transformer: (MDCAT 2024)

  1. the power input is equal to the power output
  2. the power input is less than half the power output
  3. the power input is greater than the power output
  4. the power input is more than half the power output
Show answer

Correct answer: (a) the power input is equal to the power output

An ideal transformer is lossless, so $V_pI_p=V_sI_s$.

143.The basic principle behind the operation of the transformer is (KMU MDCAT 2024)

  1. Coulomb’s law
  2. Electromagnetic induction
  3. Gas’s Law
  4. Hess’s law
Show answer

Correct answer: (b) Electromagnetic induction

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

144.A transformer uses 220V line and delivers 22A at 1800V. Current drawn from line (100% efficiency)? (NUMS MDCAT 2024)

  1. 22A
  2. 180A
  3. 200A
  4. 50A
Show answer

Correct answer: (b) 180A

Power is the same on both sides, so $1800\times22/220$ gives $180\,\mathrm{A}$.

Alternating Current

145.Phase shift between voltage and current when AC flows through capacitor is: (NUMS MDCAT 2024)

  1. V leads I by 90°
  2. I leads V by 90°
  3. V and I in phase
  4. V leads I by 45°
Show answer

Correct answer: (b) I leads V by 90°

The capacitor must be charged before a voltage appears, so the current runs a quarter cycle ahead.

Electronics

146.A diode characteristic curve is a plot between: (MDCAT 2024)

  1. current and time
  2. voltage and time
  3. voltage and current
  4. reverse voltage and forward voltage
Show answer

Correct answer: (c) voltage and current

The characteristic curve of a diode plots the current through it against the voltage across it.

147.When the PN junction is reverse-biased, its reverse current is of the order of: (KMU MDCAT 2024)

  1. Gigamperes
  2. Kiloamperes
  3. Megaamperes
  4. Microamperes
Show answer

Correct answer: (d) Microamperes

Reverse bias leaves only the small leakage of the minority carriers, of the order of microamperes.

148.The conversion of A.C. into D.C. is called rectification and the circuit is called a rectifier. Which component of electronics acts as a rectifier? (MDCAT 2024)

  1. diode
  2. transistor
  3. transformer
  4. inductor
Show answer

Correct answer: (a) diode

A diode conducts in one direction only, which is what rectification needs.

149.Full wave rectification is given by: (MDCAT 2024)

  1. one diode connected in a bridge type arrangement
  2. two diodes connected in a bridge type arrangement
  3. three diodes connected in a bridge type arrangement
  4. four diodes connected in a bridge type arrangement
Show answer

Correct answer: (d) four diodes connected in a bridge type arrangement

The bridge rectifier uses four diodes, so both halves of the cycle drive the load the same way.

150.The conversion of A.C into D.C is called rectification and circuit is called rectifier. Which component of electronics acts as a rectifier? (UHS MDCAT 2024)

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

Correct answer: (a) Diode

A diode passes current one way only, which is what rectification needs.

151.For rectification, transformer used is: (NUMS MDCAT 2024)

  1. With low input voltage
  2. With low input resistance
  3. Step up
  4. Step down
Show answer

Correct answer: (d) Step down

A rectifier works on a low voltage, so the mains is stepped down first.

Dawn of Modern Physics

152.The value of Planck's constant is: (MDCAT 2024)

  1. $6.63\times10^{-34}\ \mathrm{J\,s}$
  2. $6.63\times10^{34}\ \mathrm{J\,s}$
  3. $6.63\times10^{-24}\ \mathrm{J\,s}$
  4. $6.63\times10^{-34}\ \mathrm{J\,s^{-1}}$
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Correct answer: (a) $6.63\times10^{-34}\ \mathrm{J\,s}$

$h=6.63\times10^{-34}\ \mathrm{J\,s}$, and $E=h

153.Light propagates in space as a wave, as is evident by all of the following EXCEPT: (MDCAT 2024)

  1. interference
  2. photoelectric effect
  3. diffraction
  4. polarization
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Correct answer: (b) photoelectric effect

The photoelectric effect is the evidence for the particle model of light, not for the wave model.

154.The value of Planck constant is (UHS MDCAT 2024)

  1. 6.63x10^-34 Js
  2. 6.63x10^34 Js
  3. 6.63x10-34 Js-1
  4. 6.63x10^34 Js-1
Show answer

Correct answer: (a) 6.63x10^-34 Js

Planck’s constant is $6.63\times10^{-34}\,\mathrm{J\,s}$.

155.The de-Broglie wavelength associated with a particle moving at 10^6 m/s and having mass 10^-30 kg (UHS MDCAT 2024)

  1. 6.6x10^-10 m
  2. 1.5x10^9 m
  3. 1.9x10^-5 m
  4. 7.2x10^-8 m
Show answer

Correct answer: (a) 6.6x10^-10 m

$\lambda=h/mv=6.63\times10^{-34}/(10^{-30}\times10^{6})$, which is $6.6\times10^{-10}\,\mathrm{m}$.

156.Light propagates through space as a wave is evident by all of the following EXCEPT (UHS MDCAT 2024)

  1. Interference
  2. Photoelectric effect
  3. Diffraction
  4. Polarization
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Correct answer: (b) Photoelectric effect

Interference, diffraction and polarization are wave effects; the photoelectric effect is what showed light to be particulate.

157.The momentum of moving photon is: (KMU MDCAT 2024)

  1. mc^2
  2. λ / h
  3. h / λ
  4. zero
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Correct answer: (c) h / λ

A photon has no mass, but it carries momentum $h/\lambda$.

158.In every instant of time, wavelength associated with a freely falling body: (KMU MDCAT 2024)

  1. Decreases
  2. Increases two times
  3. Increases four times
  4. Remains constant
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Correct answer: (a) Decreases

It falls faster and faster, and $\lambda=h/mv$ shrinks as the speed grows.

159.As per 2nd photoelectric experiment, photoelectric effect does not occur if the frequency of the incident light is? (KMU MDCAT 2024)

  1. Below the threshold frequency
  2. Equals the threshold frequency
  3. Three times the threshold frequency
  4. Twice the threshold frequency
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Correct answer: (a) Below the threshold frequency

Below the threshold no photon carries enough energy to free an electron, however bright the light.

Atomic Spectra

160.Which series falls in the ultraviolet region? (MDCAT 2024)

  1. Lyman
  2. Brackett
  3. Pfund
  4. Paschen
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Correct answer: (a) Lyman

The Lyman series ends on $n=1$ and its photons are the most energetic, in the ultraviolet.

161.The potential through which an electron should be accelerated so that on collision it can lift an electron in an atom from its ground state to some higher state is known as the: (MDCAT 2024)

  1. ionization potential
  2. excitation potential
  3. string potential
  4. acceleration potential
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Correct answer: (b) excitation potential

Raising an electron to a higher level rather than removing it altogether needs the excitation potential.

162.Which series falls in ultra violet region? (UHS MDCAT 2024)

  1. Lyman
  2. Brachett
  3. Pfund
  4. Paschen
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Correct answer: (a) Lyman

The Lyman lines end on the ground level, and their photons are ultraviolet.

163.The potential through which an electron should be accelerated , so that,on collision it can lift the electron in the atom from its ground state to some higher state is known as (UHS MDCAT 2024)

  1. Ionization potential
  2. Excitation potential
  3. String potential
  4. Acceleration potential
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Correct answer: (b) Excitation potential

The potential that just lifts an electron to a higher level is the excitation potential.

164.Which of the following regarding X Rays is INCORRECT (UHS MDCAT 2024)

  1. Have higher wavelength than visible light
  2. They are part of electromagnetic spectrum
  3. They are highly penetrating in soft body tissues
  4. They are high energy photons
Show answer

Correct answer: (a) Have higher wavelength than visible light

X-rays have a far shorter wavelength than visible light, which is why they carry so much energy.

165.If an electron in the hydrogen atom jumps from second to first orbit, the emitted radiation has a wavelength of? (KMU MDCAT 2024)

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

$1/\lambda=R(1-1/4)=3R/4$, so the wavelength is $4/3R$.

Nuclear Physics

166.Mass number A refers to _____ (KMU MDCAT 2024)

  1. Number of electrons
  2. Number of nucleons
  3. Number of neutrons
  4. Number of protons
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Correct answer: (b) Number of nucleons

The mass number counts the protons and neutrons together, that is the nucleons.

167.The unit of decay constant is ; (UHS MDCAT 2024)

  1. m
  2. s
  3. s-1
  4. m-1
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Correct answer: (c) s-1

The decay constant is a probability per second, so its unit is the reciprocal second.

168.An artificial radioactive element can be made by bombarding (UHS MDCAT 2024)

  1. High energy particles on unstable elements
  2. Low energy particles on unstable elements
  3. High energy particles on stable elements
  4. Low energy particles on stable elements
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Correct answer: (c) High energy particles on stable elements

A stable nucleus struck by a fast particle is left in an unstable form that then decays.

169.The unit of the decay constant is: (MDCAT 2024)

  1. m
  2. s
  3. $\mathrm{s^{-1}}$
  4. mm
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Correct answer: (c) $\mathrm{s^{-1}}$

The decay constant is the fraction decaying per unit time, so it is measured per second.

170.If we have $N_0$ atoms of a radioactive element, then after a period of $n$ half-lives the number of atoms left behind is: (MDCAT 2024)

  1. $2^{n}N_0$
  2. $(1/2)^{n}N_0$
  3. $(N_0)^{n}$
  4. $N_0/n$
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Correct answer: (b) $(1/2)^{n}N_0$

Each half-life halves the number, so $n$ of them leave $N_0/2^{n}$.

171.If we have "No" number of any radioactive element then after a period of "n" half-lives the number of atoms left behind is (UHS MDCAT 2024)

  1. 2^n No
  2. (½)^n No
  3. (½ No)^n
  4. (2No)^n
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Correct answer: (b) (½)^n No

Each half life halves the number left, so after $n$ of them $(1/2)^n N_0$ remain.

172.Which of the following is NOT a somatic biological effect of radiation? (MDCAT 2024)

  1. skin burn
  2. loss of hair
  3. induction of cancer
  4. gene mutation
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Correct answer: (d) gene mutation

A mutation of the genes is a genetic effect, carried to the offspring; the others appear in the body of the exposed person.

173.Which of the following is NOT the Somatic biological effect of radiation? (UHS MDCAT 2024)

  1. Skin burn
  2. Loss of hair
  3. Induction of cancer
  4. Genes mutation
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Correct answer: (d) Genes mutation

A somatic effect appears in the person irradiated; a mutation in the germ cells is a genetic effect.

174.Gamma ray camera can observe radiations from the ____ that are concentrated in the organs (KMU MDCAT 2024)

  1. Atoms
  2. Isotopes
  3. Nucleons
  4. Neutrons
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Correct answer: (b) Isotopes

A gamma camera images the radioisotope that has gathered in the organ under study.

175.One rem is equal to: (NUMS MDCAT 2024)

  1. 0.01 Gy / RBE
  2. 0.01 Gy × RBE
  3. 0.01 RBE
  4. 0.01 Gy
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Correct answer: (b) 0.01 Gy × RBE

The dose equivalent in rem is the absorbed dose in rad multiplied by the relative biological effectiveness.

176.1 rad is equal to: (NUMS MDCAT 2024)

  1. 0.01 J/Kg
  2. 0.01 Kg/J
  3. 0.01 J
  4. 0.01 Kg
Show answer

Correct answer: (a) 0.01 J/Kg

One rad is $0.01\,\mathrm{J}$ absorbed in each kilogram.

177.60 kg man absorbs lethal dose of 200 rem with RBE factor of 10. Energy absorbed is: (NUMS MDCAT 2024)

  1. 9J
  2. 8J
  3. 10J
  4. 12J
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Correct answer: (d) 12J

$200\,\mathrm{rem}$ with an RBE of ten is $20\,\mathrm{rad}$, that is $0.2\,\mathrm{J\,kg^{-1}}$, and $0.2\times60$ is $12\,\mathrm{J}$.

178.Somatic effect causes: (NUMS MDCAT 2024)

  1. Gene deformation
  2. Chromosomes deformation
  3. Skin burns
  4. Eye burns
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Correct answer: (c) Skin burns

A somatic effect shows in the body irradiated; damage to the genes is a genetic effect.

179.Each person experiences background radiation dose in one year: (NUMS MDCAT 2024)

  1. 1mSv
  2. 1mGy
  3. 1Gy
  4. 1Sv
Show answer

Correct answer: (a) 1mSv

Natural background gives about a millisievert a year.

Other MDCAT past papers