Question

Whenever a magnet is moved either towards or away from a conducting coil, an emf is induced, the magnitude of which is independent of,

• A. the strength of the magnetic field
• B. the speed with which the magnet is moved
• C. the number of turns of the coil.
• D. the resistance of the coil

Answer 1

The correct option is D

the resistance of the coil

1. When a magnet is moved away or towards the coil, there will be a change in magnetic flux linked with the coil, which induces an emf in the coil.
2. According to Faraday's law of induction, The induced emf in the coil is directly proportional to the rate of change of magnetic flux linked with the coil.
3. Mathematically it can be written as, $E=-N\frac{d\phi }{dt}$ where $N$ is the number of turns in the coil, $\phi$ is the magnetic flux linked with the coil.
4. We know that $\phi =BA$. Therefore, $E=-N\frac{d\left(BA\right)}{dt}$ where $B$ is the strength of the magnetic field and $A$ is the area of cross-section of the coil.
5. Hence, emf depends on the number of turns of the coil, the strength of the magnetic field, and the area of cross-section of the coil and independent of the resistance of the coil.

Hence, option D is correct.