Question

question 3 of 25
the two ends of a coiled wire are connected to the electrodes of a lightbulb. how does the bar magnet induce a current in the wire?
a. placing the bar magnet at 90° to the axis of the coil induces a current in the wire.
b. moving the bar magnet in a circle around the lightbulb induces a current in the wire.
c. moving the bar magnet back and forth along the axis of the coil induces a current in the wire.
d. placing the bar magnet parallel to the axis and inside the coil induces a current in the wire.

Explanation:

According to Faraday's law of electromagnetic - induction, a changing magnetic flux through a coil induces an electromotive force (emf) and thus a current in the wire. Moving the bar magnet back and forth along the axis of the coil changes the magnetic flux through the coil. When the magnet is stationary relative to the coil (as in options A and D), there is no change in magnetic flux and no induced current. Moving the magnet in a circle around the light - bulb does not effectively change the magnetic flux through the coil in a way that would induce a significant current as compared to moving it along the axis of the coil.

Answer:

C. Moving the bar magnet back and forth along the axis of the coil induces a current in the wire.