A coil and a bulb are connected in series with a `dc` source, a soft iron core is then inserted in the coil. Then

Options

A. Steady state birghtness of bulb remains same
B. Steady state brightness of bulb increases
C. Steady state brightness of bulb decreases
D. Nothing can be said about the change in brightness of bulb .

Answer

A

Explanation

( c) When iron core is being inserted then there is increase in self - inductance of coil . Magnetic flux is self - inductance multiplied with current . When iron core is inserted then to resist increase in magnetic flux current in the circuit is decreased . So brightness of the bulb decreases when iron core is being inserted .