Question

A coil and a bulb are connected in series with a dc source, a soft iron core is then inserted in the coil. Then(a) Intensity of the bulb remains the same(b) Intensity of the bulb decreases(c) Intensity of the bulb increases(d) The bulb ceases to glow

Answer 1

answer : option (a) intensity of bulb remains the same.

explanation : A coil and a bulb are connected in series with direct current, when a soft iron core is inserted into the coil , there will not be any appreciable change in the magnetic flux linked with the circuit. hence, induced current equals zero and hence, intensity of bulb remains the same.

in simple way you can say that, intensity of the bulb remains constant as the reactance offered by a coil to a d.c. current is zero.


hence, option (a) intensity of bulb remains the same.