A conducting wire is bent in the form of a circle of a circle and a straight conductor AB is kept outside but near the conducting circle. The wires are in the plane of the paper. If the current flowing from A to B gradually increases in magnitude, will there be any current in the circular conductor? If so, in what direction?

Explanation

A magnetic field exists around the current carrying conductor AB. The magnetic lines of force thus generated around AB, cut the plane of the circular wire. With increase in current, the magnetic field as well as the number of lines of force linked with the circular wire increases. So, current is induced in the circular conductor, and its direction is such that the circular conductor tries to resist the increase of current in the wire AB (according to Lenz's law). This can occur only if induced current flows in clockwise direction (viewed from the upper face) in the circular conductor.