A battery is causing a large current in a solenoid (helical coil of wire). A bar magnet is held at rest nearby, aligned with the axis of the solenoid, with its south pole closest to the solenoid. The bar magnet is being repelled by the solenoid. Which of the following statements is true of the conventional current in the solenoid?
A) The current in the solenoid increases.
B) The current in the solenoid decreases.
C) The current in the solenoid is flowing counterclockwise as seen from the bar magnet.
D) The current in the solenoid is flowing clockwise as seen from the bar magnet.
E) The direction of the current in the solenoid alternates with a constant frequency.

Question

Quizplus · Accepted Answer

According to the right-hand rule, holding the solenoid in your right hand with your fingers wrapped around it in the direction of the conventional current flow, the direction of the magnetic field will be in the direction of your thumb. In this situation, the bar magnet's south pole is closest to the solenoid, which means that the magnetic field from the solenoid needs to be in the opposite direction to repel it. Therefore, the current in the solenoid must be flowing in a clockwise direction, as seen from the bar magnet. So, option D is correct.

A Battery Is Causing a Large Current in a Solenoid