Question

A small bar magnet is moved through a coil at constant speed from one end to the other. Which of the following series of observations will be seen on the galvanometer $G$ attached across the coil?

Three positions shown describe (a) the magnet's entry (b) magnet is completely inside (c) magnet's exit

• A.

  

• B.

  

• C.

  

• D.

  

Answer 1

The correct option is A

Lenz law:

1. Lenz’s law of electromagnetic induction states that the direction of the current induced in a conductor by a changing magnetic field (as per Faraday’s law of electromagnetic induction) is such that the magnetic field created by the induced current opposes the initial changing magnetic field which produced it.
2. When a bar magnet is entering with constant speed, flux will change and $emf$ is induced, so galvanometer will deflect in positive direction.
3. When the magnet is completely inside, the flux will not change, so the reading of the galvanometer will be zero.
4. When the bar magnet is making an exit, the flux will change and on $emf$ is induced in opposite direction to that of (a), so the galvanometer will deflect in negative direction.

Hence, option A is correct.