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Free Electromagnetism MCQs with Answers

1,176 Electromagnetism MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Magnetic flux density and magnetic flux describe the strength of a magnetic field and the field passing through a surface. A charged particle moving through a magnetic field experiences a force perpendicular to its velocity and may follow circular or helical motion, depending on the angle between velocity and field.

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Magnetic Flux DensityMagnetic FluxCharged Particle in a Magnetic Field
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1,176 questions · page 51 of 59

1001. To improve efficiency of transformer the flux coupling b/w primary & secondary coil should be

  • A. Small
  • B. Maximum
  • C. May be small or may be maximum
  • D. Zero

Explanation: This option states that the flux coupling between the primary and secondary coil should be at its maximum to improve efficiency.

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Correct answer: Maximum

1002. Primary secondary coils of a transformer have 50 and 200 turns respectively. when primary is connected to 9 volt battery secondary voltage is:

  • A. 90
  • B. 36
  • C. 18
  • D. Zero

Explanation: Voltage a battery is D.C but transformer operates on A.C not on D.C

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Correct answer: Zero

1003. A copper ring having a cut such as not to from a complete loop is held horizontally and a bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet is :

  • A. g
  • B. Less than g
  • C. More than g
  • D. 0

Explanation: As the ring is not continuous, the emf will generate in the ring but due to incomplete circuit, no current will flow.

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Correct answer: g

1004. In a step-up transformer the turns ratio is 1:2. A cell of emf 15V is connected across the primary. The voltage across secondary is

  • A. 3.0V
  • B. 0.7V
  • C. Zero
  • D. 1.5V

Explanation: The transformer does not work for DC. It works only for AC so option C is correct

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Correct answer: Zero

1005. A conducting ring is placed around the core of an electromagnet as shown in the figure. When key K is pressed , the ring :

  • A. Remains stationary
  • B. Is attracted towards the electromagnet
  • C. Jumps out of the core
  • D. None of these

Explanation: According to lenz's law the ring will jump out of the core . As when key is pressed current starts to flow in an electromagnet, so ring…

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Correct answer: Jumps out of the core

1006. when a magnet is moved into the coil of wire shown, there is a small reading on the sensitive meter. Which change would increase the size of the reading?

  • A. Moving the magnet faster
  • B. Pilling the magnet out
  • C. Pushing in the S-pole
  • D. Unwinding some of the turns of wire

Explanation: Induced emf can be increased by I. Using large no. of turns 2. Using stronger B 3. Moving the loop faster

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Correct answer: Moving the magnet faster

1007. The rod of unit length 1m is moving at through a magnetic field of IT. If velocity of rod is I ms-1, then induced emf in the rod will be given by:

  • A. 1V
  • B. 0.5V
  • C. 0.25V
  • D. 0.6V

Explanation: Using the formula E = VBL V=1 ms-1 B=1T L=1m 1×1×1= 1 volts

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Correct answer: 1V

1008. A metal rod of length 30cm is moving at a speed of 0.5ms-1 in a direction perpendicular to a 0.25T magnetic field. Find the emf produced in the rod.

  • A. 3.13 x 10^-2V
  • B. 4.13 x 10^-2V
  • C. 3.75 x 10^-2V
  • D. 4.75 x 10^-2V

Explanation: Explanation is given below: Using formula E= VBL V= 0.5 B= 0.25 L= 30cm converting to meters = 30/100= 0.3m 0.5×0.25×0.3 = 3.75×10-2 V

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Correct answer: 3.75 x 10^-2V

1009. Find the length of a conductor which is moving with a velocity 0.4m/s in a magnetic field of 8T, inducing an emf of 20V if magnetic field, velocity and length of conductor are mutually perpendicular to each other.

  • A. 50m
  • B. 5m
  • C. 6.25m
  • D. 0.5m

Explanation: Explanation is giving below: Using the formula : E= VBL

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Correct answer: 6.25m

1010. Quantity that remains unchanged in a transformer is :

  • A. Voltage
  • B. Current
  • C. Frequency
  • D. None of these

Explanation: Time period, frequency and phase remain the same at the output of the transformer.

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Correct answer: Frequency

1011. The source of induced e.m.f is:

  • A. Cell
  • B. Battery
  • C. Interaction between stationary magnet and coil
  • D. Relative motion between magnet and coil

Explanation: The source of induced electromotive force (e.m.f.) is D) Relative motion between a magnet and a coil.

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Correct answer: Relative motion between magnet and coil

1012. When the coil and a bar magnet are placed very close to each other, then the value of their induced e.m.f will be:

  • A. Maximum
  • B. Positive
  • C. Negative
  • D. Zero

Explanation: The correct answer based on the given options would be D) zero, assuming the scenario involves the coil and bar magnet being very close…

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Correct answer: Zero

1013. The unit of induced e.m.f is:

  • A. Ampere
  • B. Volt
  • C. Watt
  • D. Weber

Explanation: The unit of induced electromotive force (emf) is the volt (V). The induced emf is measured in volts, which represents the electrical…

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Correct answer: Volt

1014. The law of electromagnetic induction was introduced by:

  • A. Maxwell
  • B. Faraday
  • C. Lenz
  • D. Fleming

Explanation: Law of electromagnetic induction was introduced by Faraday and is known as Faraday's law of electromagnetic induction.

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Correct answer: Faraday

1015. According to Faraday's law of electromagnetic induction, the induced e.m.f depends upon

  • A. Minimum magnetic flux
  • B. Maximum magnetic flux
  • C. Change in magnetic flux
  • D. Rate of change of magnetic flux

Explanation: Faraday's law states that a current will be induced in a conductor which is exposed to a changing magnetic field.Any change in the…

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Correct answer: Rate of change of magnetic flux

1016. Lenz's law of electromagnetic induction explains:

  • A. The production of induced e.m.f
  • B. Magnitude of induced e.m.f.
  • C. Direction of induced e.m.f
  • D. Both magnitude and direction of induced e.m.f

Explanation: Lenz's law prominently focuses on determining the direction of the induced emf.

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Correct answer: Direction of induced e.m.f

1017. Lenz's law is related to the law of conservation of:

  • A. Momentum
  • B. Energy
  • C. Mass
  • D. Charges

Explanation: Lenz's law is closely associated with the conservation of energy. It describes how the induced current or electromotive force in a circuit…

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Correct answer: Energy

1018. The mutual inductance of two coil is maximum when the coils are

  • A. Parallel to each othe
  • B. Perpendicular to each other
  • C. Facing each other
  • D. Touching each other

Explanation: The mutual inductance of two coils is at its maximum when the coils are coaxially wound one on top of the other.

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Correct answer: Parallel to each othe

1019. When a current changes in a coil from 4A to 6 A in 0.05s and it induces an e.m.f of 8 V. The co-efficient of self-inductance is:

  • A. 0.1H
  • B. 0.2H
  • C. 0.4H
  • D. 0.8H

Explanation: The calculation is as follows: L = E/(∆I÷∆t) = 8/(2÷0.05) = 8/40 = 0.2H

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Correct answer: 0.2H

1020. The unit of inductance is:

  • A. Weber
  • B. Tesla
  • C. Henry
  • D. Watt

Explanation: The unit of self-inductance is the Henry (H), named after Joseph Henry.

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Correct answer: Henry
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