Question

Which of the following will cause an induced current in a coil of wire?the constant field of the earth passing through the coila magnet resting near the coila magnet being moved into or out of the coila wire carrying a constant current near the coil

Answer 1

magnet being moved into or out of the coil

Step-by-step explanation:

Electromagnetic induction occurs when there is a change in the magnetic flux through a closed coil of wire; when this occurs, an emf (electromotive force) is induced in the coil, and it is given by

`\epsilon= -(\Delta \Phi)/(\Delta t)`

where

`\Delta \Phi` is the variation of magnetic flux through the wire

`\Delta t` is the time elapsed

From the formula, we see that an emf (and so, a current) is induced in the coil of wire only if there is a change in the magnetic flux through the coil. Among the options given, only the following one:

magnet being moved into or out of the coil

involves a change in the magnetic flux through the coil (because by moving the magnet into and out the coil, we change the strenght of the magnetic field crossing the area enclosed by the coil), so this is the right answer.