Question

A circuit consists of a conducting movable bar and a lightbulb connected to two conducting rails as shown in the figure below. An external magnetic field is directed perpendicular to the plane of the circuit. Which of the following actions will make the bulb light up? (Select all that apply.)


a.The bar is moved to the left.
b.The bar is moved to the right.
c.The magnitude of the magnetic field is increased.
d.The magnitude of the magnetic field is decreased.
e.The bar is lifted off the rails.

Answer 1

According to faradays law of electromagnetic induction whenever there is a rate of change of magnetic flux assosiated with a coil, an induced emf developed in it. this induced emf developes an induced current in the coil.

As shown from the diagram an induced current developes when the bar moves to left or right or the magnetic field increases

or decreses.

If the bar is lift off from rails, there is no change in magnetic field no induced current in the circuit and bulb is not glow. The light bulb glows in cases of (a), (b),(c) and (d)