The sketches below show a circular coil and a permanent magnet; the arrows indic

Question

The sketches below show a circular coil and a permanent magnet; the arrows indicate both the magnitude and the direction of the velocities of the magnet and coil. For each situations, determine the direction of the induced current in the loop as viewed from the right. First determine if the flux through the loop is increasing, decreasing or unchanged. If the flux is increasing, then the induced current produces a field that is opposite in direction to the field by the bar magnet. If the flux is decreasing, then the induced current produces a field that is in the same direction to the field by the bar magnet. If the flux is not changing, then there is no induced current. Use the right hand rule (current and magnetic field) to determine the direction of the induced current.

Explanation / Answer

1. Here bar magnet is moving but cross sectional area of the loop is parallel to the magnetic field lines, Hence = 90

=BAcos90 = 0

No flux no current

2. The bar magnet or the loop is not moving hence there is no change in the magnetic flux. So no current in the coil.

3. The loop is moving away from the bar magnet hence the magnetic flux decreases. So induced magnetic field is directed to the right. Applying right hand rule direction of the current is counterclockwise.

4. The loop is moving faster towards the bar magnet hence the magnetic flux increases. So induced magnetic field is directed to the right ( opposite the bar magnet). Applying right hand rule direction of the current is counterclockwise.

5. Bar magnet as well as the loop are moving away from each other with equal magnitude of velocity. Hence flux decreases as a result induced magnetic field will be in the right side. By right hand rule induced current will be counterclockwise.

6. south pole is approaching the loop which is steady. Induced magnetic field will be to the left. So direction of induced current will be clockwise .

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