Question

two circular coils a and b of insulated wires are kept close to each other coil a is connected to a galvanometer while coil b is connected to a battery through a key what will u observe in coil a if(a) current is passed through coil b by plugging the key(b) the curren is stopped by removing the plug from the key?(c) both the coils are moved in the same direction with the same speed? explain your answer mentioning the name of the phenomena involved

Answer 1

(i) When current ismade to pass through coil B, by plugging the key in, for that instant, the galvanometer connected to coil A shows a deflection, i.e., current passes through coil A as well.
(ii) When current isstopped through coil B by taking the plug of the key out, for that instant, the galvanometer connected to coil A again shows a deflection, this time, however, in the opposite direction.That is, a current passes through coil A in the opposite direction.The observations are made because whenever we change the current inthe coil B, the magneticfield associated with itand the coil A in its proximitychanges. At the very instant ofplugging the key inor taking the plug out, thereis an instantaneous flow of current and a change in the magneticfield associated with the coil B. During this instantaneous moment, the current incoil B reaches from zero to the maximum or from the maximum to zero. This changingmagneticfield of coil B induces a current in the coil A.The phenomenon is known aselectromagnetic induction.