Question

The phenomenon of electromagnetic induction is –
A) The process of charging a sphere.
B) The process of producing magnetic fields in a coil.
C) The process of producing induced current in a coil whenever there is a relative motion between the coil and the magnet.
D) The process of producing cooling effects.

Answer 1

We are asked to find the correct definition or the understanding on the electromagnetic induction. We need to understand the phenomenon of electromagnetic induction and the Faraday’s law that govern how to solve this problem easily.

Complete answer:
Electromagnetic induction is the phenomenon in which an electromotive force can be induced in a conductor by the relative motion or the change in the magnetic flux with time. According to Faraday's law of electromagnetic induction, an electromagnetic force is induced in a coil of a conductor which is placed in a magnetic field is equal to rate of change of magnetic flux. It is given as –

& \varepsilon =-\dfrac{d\phi }{dt} \\\ & \Rightarrow \varepsilon =-\dfrac{d}{dt}B.A \\\ & \therefore \varepsilon =-\dfrac{d}{dt}BA\cos \theta \\\ \end{aligned}$$ So, any change in the magnetic field, area of the coil or the angle relation between the magnetic field and the area will cause an emf in the coil. From the above discussion, we can understand that the electromagnetic induction is the phenomenon in which a current is produced by induction of electromotive force induced in the coil by the relative motion of the coil and the magnetic field or the rate of change of magnetic flux. So, the phenomenon of electromagnetic induction is the process of producing induced current in a coil whenever there is a relative motion between the coil and the magnet. This is the required solution. **The correct answer is option C.** **Note:** The negative sign in Faraday's law denotes that the electromotive force produced in the coil is due to the opposing effect of the conducting coil against the change produced by the changing magnetic flux in the system. This is Lenz's law.