Question

In the following diagram an arrow shows the motion of the coil towards the bar magnet.
(i) State in which direction the current flows: $A$ to $B$ or $B$ to $A$?

(ii) Name the law used to come to the conclusion.

Answer 1

(i) The direction of the current is from$A$ to $B$.

(ii) The law is used to come to the conclusion is Lenz's law.

Lenz's law states that when an emf is generated by a change in magnetic flux, the polarity of the induced emf is such, that it produces a current, i.e., magnetic field opposes the change which produces it. Here to oppose it, the current has to be produced in such a way to have a north polarity on the right side of the coil (in the figure given) and hence, south polarity in the left side of the coil. If north polarity has to be created in the coil, then the current has to flow in the anti-clockwise direction on the right side of the coil. That means the electric current has to flow towards $B$ from $A$. So current flows from $A$ to $B$.