Chapter 21, Problem 3Q

To determine

To Explain: Whether a current will be induced in the wire or not. Also, the current induced when the magnet is held steady within the ring and direction of a current.

Answer to Problem 3Q

Yes, current will be induced in the wire.

No, a current will not be induced when the magnet is held steady within the ring.

The direction of current is counter clockwise.

Explanation of Solution

Introduction:Faraday’s law of induction is the fundamental law of electromagnetism. According to this law,

  $EMF=-N\frac{\Delta {\varphi }_B}{\Delta t}$

Minus sign represents direction the induced EMF acts. If $N$ is large, then the induced EMF and induced current will also be large.

According to the question, a current will be induced in the wire. A clockwise current is created because the magnetic flux is changing. By using the Lenz’s law, obtain the direction of the current. It creates a magnetic field that reduces the magnetic flux.

In the given experiment,zero current will be induced because the magnetic flux is not varying (or changing). Also, a counter clockwise (direction) current will be created because the magnetic flux is varying. By the same law (Lenz’s law) obtain the direction of the current which forms a magnetic field that reduces the magnetic flux.

Therefore, current will be induced in a ring when anyone move the south pole towards the ring. Also, current will be not induced in a ring when magnet is held steady within ring.