questions on electromagnetic induction

Questions on Electromagnetic Induction with answers

Jan 13 • Resources • 45821 Views • 58 Comments on Questions on Electromagnetic Induction with answers

Electromagnetic induction is one of the major portion of many subjects like physics, basic electrical and others. Many questions are asked in academic and competitive exam and even in interviews of many high profile companies. So it is required to have an in-depth knowledge of the same. So here are some very very important questions on electromagnetic induction and its applications with answers containing proper diagrams.

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Q1: What do you mean by Electromagnetic induction ?

Ans: The finding that electric current can produce magnetic fields led to the idea that magnetic fields could produce electric currents. The production of emfs and currents by the changing magnetic field through a conducting loop is called magnetic induction.


electromagnetic induction

Generation of current through electromagnetic induction

Q2: State and explain Lenz’s law in relation with Electromagnetic Induction?

Ans: Lenz’s law infact describes that in order to produce an induced emf or induced current some external source of energy must be supplied otherwise no current will induce.

Lenz’s law states that-

“The direction of induced current is always such as to oppose the cause which produces it”.


   Consider a bar magnet and a coil of wire.
  1. When the N-pole of magnet is approaching the face of the coil, it becomes a north face by the induction of current in anticlockwise direction to oppose forward motion of the magnet.
Lenz law
   b. When the N-pole of the magnet is receding the face of the coil becomes a south pole due to a    clockwise induced current to oppose the backward motion.
Lenz law

Q3: State Faraday’s Law of EMI.

Ans: Faraday’s Law states that “When magnetic flux changes through a circuit, an emf is induced in it which lasts only as long as the change in the magnetic flux through the circuit continues”.

Quantitatively, induced emf is directly proportional to the rate of change of magnetic flux through
the coil. i.e.

Average emf = -NDf/Dt

Where N = number of turns in the coil.

The negative sign indicates that the induced current is such that the magnetic field due to it opposes the magnetic flux producing it.
Q4: Depict/Draw diagrams showing Left hand and Right hand thumb rule showing directions of quantities in EMI.
Left hand thumb ruleRight hand thumb rule

Q5: What is the difference between Magnetic Field and Magnetic Flux?

Ans: A magnetic field is the area surrounding a magnet within which the effects of that field may be observed.

A magnetic field is represented by imaginary lines of force that we call magnetic flux. Magnetic flux is measured in webers; the intensity of the magnetic flux is called magnetic flux density which is defined as the flux per unit area, measured in webers per square metre, which is given the special name, the tesla.

Q6: Explain differences between Magnetic field and Electric field?

Ans:1. An electric field is a field of force, surrounding a charged particle, while a magnetic field is a field of force surrounding a permanent magnet, or a moving charged particle.

2. The strength of an electric field is expressed in Newtons per Coulomb, or Volts per meter, while a magnetic field strength is expressed in Gauss or Tesla.

3. The force of an electric field is proportional to the electric charge, while the magnetic field is proportional to the electric charge as well as the speed of the moving charge.

4. Electric and magnetic fields oscillate at right angles to one another.

Q7: Explain what is a transformer?

A transformer makes use of Faraday’s Law and the ferromagnetic properties of an iron core to efficiently raise or lower AC voltages. It of course cannot increase power so that if the voltage is raised, the current is proportionally lowered and vice versa.




An ideal transformer

Q8: Explain Eddy Currents.

Ans: An eddy current is a circular current that flows in a solid conductor, such as sheets of metal or rods. When a changing magnetic field is somehow applied to such a conductor, electromagnetic induction occurs. However, since the charges are not bounded by a narrow conductor, the currents flow in circles called eddy currents. The eddy current flows in a closed loop and acts like the current in a coil or solenoid that produces its own magnetic field.

Q9: Why is EMI regulated?

Ans: EMI is regulated to allow today’s sensitive equipment to function properly without suffering degradation in performance due to interference generated by the equipment itself as well as the interference generated by other electronic devices. The EMI spectrum is a limited natural resource that must be maintained to allow reliable radio frequency communications. The successful regulation of EMI interference will allow future electronic devices to operate as defined, in the intended environment, without suffering any degradation in performance due to interference, and without disrupting the performance of other equipment.

Q10: Explain differences between AC and DC.


Alternating CurrentDirect Current
Amount of energy that can be carried:Safer to transfer over longer city distances and can provide more powerVoltage of DC cannot travel very far until it begins to lose energy
Flow ofElectrons:Electrons keep switching directions- forward and backwardElectrons move steadily in one direction or ‘forward’
Cause of the direction of flow of electrons:Rotating magnet along the wireSteady magnetism along the wire
Frequency:The frequency of alternating current is 50Hz or 60Hz depending upon the country.The frequency of direct current is zero.
Direction:It reverses its direction while flowing in a circuitIt flows in one direction in the circuit
Current:It is the current of magnitude varying with timeIt is the current of constant magnitude


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58 Responses to Questions on Electromagnetic Induction with answers

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    a bar rotating in a magnetic field B and there is a loop with ross section A what is the emf in the loop??

  52. Lee says:

    having difficulties in tackling questions on electromagnetic induction

  53. Sumit Mukherjee says:

    Electromagnetic induction states that the logic of producing magnetic field through electric field and vice-vesra. For that EMI and to solve the problems regarding the above, we are having several formulas like Lenz’s law or Faraday’s Law etc. So, i believe that all of us mostly who are belonging from the science sector please read the following article…

  54. SANJANA KUMARI says:

    Electromagnetic Induction is a very important topic which related to Physics and Electrical. so this topic should be taught in a very good way so that students understand all the utilities of this principle and apply them in various projects during their technical studies. In electromagnetic induction, if we kept the bar magnet stationary and moved the coil back and forth within the magnetic field an electric current would be induced in the coil. Then by either moving the wire or changing the magnetic field we can induce a voltage and current within the coil and this process is known as Electromagnetic Induction and is the basic principal of operation of transformers, motors and generators. I think the article is very good for beginners for the topic concern.

  55. Shilpa Ranjan says:

    Electromagnetic induction is one of the topic which is studied in electrical papers. This article consists of important concepts of electromagnetic in simple language.

  56. sakshi chaudhary says:

    this article give valuable knowledge about the basic terms used in physics like electromagnetic induction, transformers,concept behind eddy current,,,

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