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:

Step1: Magnet moving quickly into solenoid

When the magnet is moved quickly into the right - end of the solenoid, there is a large change in magnetic flux. According to Faraday's law of electromagnetic induction ($\epsilon=-N\frac{\Delta\varPhi}{\Delta t}$), a large induced emf and thus a large current is generated.

Step2: Magnet held in solenoid

When the magnet is held in the solenoid for 3 s, there is no change in magnetic flux ($\Delta\varPhi = 0$). So, by Faraday's law, the induced emf is zero and the current drops to zero.

Step3: Solenoid moving slowly away from magnet

When the solenoid is moved slowly to the left away from the magnet, there is a change in magnetic flux but at a slower rate compared to the first step. So, a smaller induced emf and current are generated. Also, according to Lenz's law, the direction of the induced current will be opposite to the direction of the first - generated current as the change in magnetic flux is in the opposite sense compared to the first step.

Answer:

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