Question

d. explain your use of a hand rule to determine the magnetic poles of the permanent magnet and the induced poles of the solenoid in the diagram below. (2 marks)

Explanation:

To determine the poles: First, for the induced current in the solenoid, use the Lenz's Law (and right - hand rule for solenoid). The solenoid has N (top) and S (bottom) as shown. When the permanent magnet moves down, the induced current in the solenoid creates a magnetic field to oppose the change (Lenz's Law). Using the right - hand grip rule for the solenoid (curl fingers in current direction, thumb points to N - pole), we can find the current direction. Then, for the permanent magnet, since the solenoid's top is N, the permanent magnet's bottom (near solenoid's N) should be S (opposite, due to repulsion/opposition in induction), so the permanent magnet's top is N and bottom is S. The hand rule (right - hand grip for solenoid: hold solenoid, fingers follow current, thumb is N - pole) helps find induced poles; for the permanent magnet, the direction of its movement and the induced field of solenoid (opposing) tell us its poles (bottom S, top N as it moves down towards solenoid's N, so like poles repel? Wait, no—Lenz's Law: the induced field opposes the motion. If the magnet is moving down, the solenoid's top pole should repel it (so solenoid top is N, magnet bottom is S). So using right - hand rule on solenoid: current direction (from G's connection) – if we assume the current flows such that when we grip the solenoid with right hand, thumb is N (top), fingers curl in current direction. Then, the permanent magnet's bottom is S (to be repelled by solenoid's N as it moves down), so permanent magnet top is N, bottom is S.

Answer:

To determine the poles:

1. Induced Poles of Solenoid: Use the right - hand grip rule (for solenoids): Curl the right hand’s fingers in the direction of the induced current (determined by Lenz’s Law, opposing the magnet’s motion). The thumb points to the solenoid’s north (N) pole (top, as shown: N at top, S at bottom).
2. Poles of Permanent Magnet: By Lenz’s Law, the solenoid’s induced field opposes the magnet’s downward motion. Since the solenoid’s top is N, the permanent magnet’s bottom (near the solenoid) must be S (to create repulsion, opposing the downward motion). Thus, the permanent magnet’s top is N, bottom is S.

(The hand rule (right - hand grip) for the solenoid gives its induced N (top); the magnet’s poles are deduced from Lenz’s Law (opposition to motion: magnet’s bottom = S, top = N).)