Question

lionel explores electromagnetic induction using the procedure shown.

1. move the magnet quickly into the right end of a solenoid.
2. hold the magnet in the solenoid for 3 s.
3. move the solenoid slowly to the left away from the magnet.

what should lionel observe during his investigation?
a large current forms, drops to zero, then remains at zero.
a large current forms, drops to zero, then a smaller current forms in the opposite direction.
a large current forms, drops to zero, then a smaller current forms in the same direction.
a small current forms, drops to zero, then a larger current forms in the same direction.

Explanation:

1. Step 1: Analyze Step 1 of the Procedure

When the magnet is moved quickly into the solenoid, the magnetic flux through the solenoid changes rapidly. By Faraday’s law of electromagnetic induction, a large induced current is produced.

1. Step 2: Analyze Step 2 of the Procedure

When the magnet is held stationary inside the solenoid, the magnetic flux through the solenoid is constant (no change in flux). By Faraday’s law, no induced current is produced, so the current drops to zero and remains zero while the magnet is held.

1. Step 3: Analyze Step 3 of the Procedure

When the solenoid is moved slowly away from the magnet, the magnetic flux through the solenoid decreases, but at a slower rate than when the magnet was moved quickly in (since the solenoid’s motion is slow). By Lenz’s law, the induced current will oppose the change in flux. Since the flux is decreasing (opposite to the first step, where flux increased), the induced current will be in the opposite direction to the first current. Additionally, because the motion is slow, the rate of flux change is smaller, so the induced current is smaller than the initial large current.

Answer:

B. A large current forms, drops to zero, then a smaller current forms in the opposite direction.