Faraday’s Law of Electromagnetic Induction

Faraday’s Law of Electromagnetic Induction MDCAT MCQs with answers

37 past paper MCQs on Faraday’s Law of Electromagnetic Induction, from the Electromagnetic Induction unit of MDCAT Physics. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

Read the notes first Practise the unit as a quiz

1.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
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Correct answer: (b) 12 V

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

2.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. $\mathrm{N\,m\,A^{-2}\,s}$
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Correct answer: (c) $\mathrm{N\,m\,A^{-1}\,s^{-1}}$

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

3.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
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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.

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

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

5.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
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Correct answer: (b) Faraday's law

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

6.A coil is rotated in a uniform magnetic field about an axis perpendicular to the field. The induced emf is maximum when the plane of the coil is: (UHS MDCAT 2017)

  1. parallel to the field
  2. perpendicular to the field
  3. at $45^{\circ}$ to the field
  4. none of the given options
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Correct answer: (a) parallel to the field

With the plane along the field the flux through the coil is zero and its rate of change is greatest, so the emf is at its peak.

7.The cause of an induced emf is the: (UHS MDCAT 2017)

  1. rate of change of magnetic flux
  2. decrease in magnetic flux
  3. increase in magnetic flux
  4. change in magnetic flux
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Correct answer: (a) rate of change of magnetic flux

Faraday law fixes the emf as $-N\Delta\Phi/\Delta t$, so it is the rate at which the flux changes, not merely the change.

8.Basic requirement for induced emf is: (NUMS MDCAT 2025)

  1. Flux linked to coil
  2. No flux linked to coil
  3. Coil should be circular
  4. Change in flux links to the coil
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Correct answer: (d) Change in flux links to the coil

An emf appears only while the flux through the coil is changing.

9.EMF induced is zero when plane of coil is: (NUMS MDCAT 2025)

  1. Perpendicular to B
  2. Parallel to B
  3. Antiparallel
  4. None of these
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Correct answer: (a) Perpendicular to B

With the plane perpendicular to the field the flux is already at its maximum, so it is momentarily not changing.

10.161.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
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Correct answer: (b) 1

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

11.162.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.

12.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
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Correct answer: (a) 12 V

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

13.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
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Correct answer: (a) Number of turns

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

14.Q.163 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 ? (UHS MDCAT 2023)

  1. 10 v
  2. 12 v
  3. 14 v
  4. 16 v
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Correct answer: (b) 12 v

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

15.Q.164 The unit of Δφ/Δt can be written as ? (UHS MDCAT 2023)

  1. NmA^-2s^-1
  2. NmAs^-1
  3. NmA^-1s^-1
  4. NmA^-2s1
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Correct answer: (c) NmA^-1s^-1

The rate of change of flux is an emf, that is a volt, and a volt is $\mathrm{N\,m\,A^{-1}\,s^{-1}}$.

16.Q.166 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 ? (UHS MDCAT 2023)

  1. Rotated about a north-south axis
  2. Rotated about an east-west axis
  3. Moved rapidly, without rotation, toward the east
  4. Moved rapidly, without rotation, toward the south
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Correct answer: (b) Rotated about an east-west axis

Turning about the east-west axis sweeps the plane of the hoop right through the north-south field lines.

17.In Fleming’s right hand rule the middle finger indicates: (SZABMU MDCAT 2023)

  1. Force
  2. Magnetic field
  3. Induced current
  4. Volt
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Correct answer: (c) Induced current

Thumb for motion, first finger for field, second finger for the induced current.

18.In Fleming's right hand rule, the second finger indicates: (NUMS MDCAT 2023)

  1. Force
  2. Magnetic field
  3. Induced current
  4. Motion
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Correct answer: (c) Induced current

Thumb for motion, first finger for field, second finger for the induced current.

19.A current generator is a device that converts: (NUMS MDCAT 2023)

  1. Mechanical energy into electrical energy
  2. Chemical energy into mechanical energy
  3. Sound energy into mechanical energy
  4. Electrical energy into mechanical energy
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Correct answer: (a) Mechanical energy into electrical energy

A generator turns the work done in rotating the coil into electrical energy.

20.The expression for the emf produced by A. C. generator is? (UHS MDCAT 2023)

  1. NωAB Sinθ
  2. NωAB Cosθ
  3. NωAB
  4. ILB Cosθ
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Correct answer: (a) NωAB Sinθ

The emf of a rotating coil is $NAB\omega\sin\theta$.

21.The induced emf produced in the coil is sometimes called as? (UHS MDCAT 2023)

  1. Self-inductance
  2. Back emf
  3. Motional emf
  4. Mutual inductance
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Correct answer: (b) Back emf

The emf induced in a coil by its own changing current opposes that current, so it is called the back emf.

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

  1. 0
  2. 1
  3. 2
  4. 3
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Correct answer: (c) 2

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

23.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
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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.

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

  1. Transformers
  2. Inductors
  3. Capacitors
  4. Motor
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Correct answer: (d) Motor

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

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

  1. AC voltage
  2. High AC voltage
  3. DC voltage
  4. Low AC voltage
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Correct answer: (c) DC voltage

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

26.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
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Correct answer: (c) Electrical energy

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

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

  1. Mechanical to electrical
  2. Electrical to mechanical
  3. Electrical to heat
  4. Heat to electrical
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Correct answer: (a) Mechanical to electrical

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

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

  1. Constant
  2. Decrease
  3. Increase
  4. Continuously changing
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Correct answer: (d) Continuously changing

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

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

  1. Induced current
  2. Direct current
  3. Polarized current
  4. No current
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Correct answer: (a) Induced current

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

30.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
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Correct answer: (b) current

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

31.Motional e.m.f induced in a coil is dependent on? (PMC Practice 2021)

  1. Magnetic field
  2. Orientation
  3. Length
  4. All of these
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Correct answer: (d) All of these

$\varepsilon=BLv$ with the orientation, so the field, the length and the angle all enter.

32.A metal rod of length 4 m, velocity 5 m/s and magnetic field 0.5 T will have an induced EMF of: (PMC Practice 2021)

  1. 10 V
  2. 20 V
  3. 30 V
  4. 4 V
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Correct answer: (a) 10 V

$\varepsilon=BLv=0.5\times4\times5$, that is $10\,\mathrm{V}$.

33.If a stationary bar magnet is placed near a coil so that maximum lines of force passes through the coil, the galvanometer shows: (PMC MDCAT 2020)

  1. Maximum current
  2. Minimum current
  3. No current
  4. Intermediate value of current
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Correct answer: (c) No current

An emf appears only while the flux is changing, and a stationary magnet changes nothing.

34.If we change the magnetic flux linking a coil by rotating the coil in a constant magnetic field, the rate of change of this flux is: (UHS MDCAT 2019)

  1. Proportional to the emf produced in it
  2. Proportional to the material Of the coil
  3. Proportional to the resistance of the coil
  4. Proportional to the change in magnetic field
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Correct answer: (a) Proportional to the emf produced in it

Faraday’s law makes the emf equal to the rate of change of flux.

35.A metal rod of length 10.0 cm is moving at a speed of 0.5 ms-1 in a direction perpendicular to a 0.20 T magnetic field. Find the emf produced in the rod. (UHS MDCAT 2018)

  1. 2.0 x 10-3V
  2. 0.50 x 10-2V
  3. 1.0 x 10-2V
  4. 1.0 x 10-3V
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Correct answer: (c) 1.0 x 10-2V

$\varepsilon=BLv=0.20\times0.10\times0.5$, that is $1.0\times10^{-2}\,\mathrm{V}$.

36.The cause of induced emf is: (UHS MDCAT 2017)

  1. Rate of change of magnetic flux
  2. Decrease in magnetic flux
  3. Increase in magnetic flux
  4. Change in magnetic flux
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Correct answer: (d) Change in magnetic flux

An emf appears whenever the flux through the circuit changes.

37.A coil is rotated in a uniform magnetic field about an axis perpendicular to the field. The emf induced in the coil would be maximum when the plane of the coil is: (UHS MDCAT 2017)

  1. Parallel to the field
  2. Perpendicular to the field
  3. At 45˚ to the field
  4. None of the given options are correct
Show answer

Correct answer: (a) Parallel to the field

With the plane along the field the flux is momentarily zero and changing fastest.

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