Question

Which of the following will cause an induced current in a coil of wire? A. A wire carrying a constant current near the coil B. A magnet being moved into or out of the coil C. The constant field of the Earth passing through the stationary coil D. A magnet stationary resting near the coil

Answers

1. Answer:

B. A magnet being moved into or out of the coil

Explanation:

Faraday law of electromagnetic induction states that when there is change in flux , an emf is produced . Among the given instances , only in case of B , flux is changing . So current will be induced in the coil . We shall see how it takes place .

A wire carrying constant current will produce magnetic flux in nearby coil but there is no change in flux because current as well as position of wire with respect to coil are  not changing  .

Passing of magnetic field through a stationary coil produces flux in the coil but here too there is no change in flux so no current will be induced .

A magnet positioned near a coil creates magnetic flux in the coil but the magnitude of flux remains constant so no change in flux and no creation of induced current .