 # A bar magnet is held stationary while a circular loop of wire is moved toward the magnet at constant velocity at position A as in Figure CQ 20.1. The loop passes over the magnet’s center at position B and moves away from the magnet at position C . Viewing the loop from the left as indicated in the figure, find the direction of the induced current in the loop (a) at position A and (b) at position C . (c) What is the induced current in the loop at position B ? Indicate the directions as either CW (for clockwise) or CCW (for counterclockwise). Figure CQ20.1 ### College Physics

11th Edition
Raymond A. Serway + 1 other
Publisher: Cengage Learning
ISBN: 9781305952300 ### College Physics

11th Edition
Raymond A. Serway + 1 other
Publisher: Cengage Learning
ISBN: 9781305952300

#### Solutions

Chapter
Section
Chapter 20, Problem 1CQ
Textbook Problem

## A bar magnet is held stationary while a circular loop of wire is moved toward the magnet at constant velocity at position A as in Figure CQ20.1. The loop passes over the magnet’s center at position B and moves away from the magnet at position C. Viewing the loop from the left as indicated in the figure, find the direction of the induced current in the loop (a) at position A and (b) at position C. (c) What is the induced current in the loop at position B? Indicate the directions as either CW (for clockwise) or CCW (for counterclockwise). Figure CQ20.1

Expert Solution

(a)

To determine
To find the direction of current induced at position A of the circular loop

The direction of current induced in the circular loop is anti-clock wise direction.

### Explanation of Solution

According to Lenz’s law whenever the magnetic flux associated with loop changes the emf induces and hence current flows through the coil. And this current flow in such a way that the change in magnetic flux opposes by flowing the current through the loop

When the loop is at position A the magnetic flux associated with the loop changes and its direction is from north south pointing towards the right so it will opposes these change by flowing a current in anti-clock wise direction such that the magnetic field induced due to this current will be pointing towards left

Conclusion: The direction of current induced in the circular loop is anti-clock wise direction.

Expert Solution

(b)

To determine
To find the direction of current induced at position B of the circular loop.

There is no current through the loop

### Explanation of Solution

The change in magnetic flux associated with a loop changes results the induced emf and current in the loop and this current will flow in such way that opposes the cause of change. When circular loop is at position B there is no change of magnetic flux associate with it therefore current flow through the loop is zero.

Conclusion: There is no current through the loop

Expert Solution

(c)

To determine
To find the direction of current induced at position C of the circular loop

The direction of current induced in the circular loop at position C is clock wise direction

### Explanation of Solution

The current flow in such a way that the change in magnetic flux opposes by flowing the current through the loop by Lenz’s law. At position C the flow of current through the loop is clock wise since the loop is moving away from the vicinity of magnetic flux so it will try to oppose this and as a result increase the magnetic field in the same direction as that of magnetic field present initially.

Conclusion: The direction of current induced in the circular loop at position C is clock wise direction

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