A light bulb and a solenoid are connected in series across an ac source of voltage. Explain, how the glow of the light bulb will be affected when an iron rod is inserted in the solenoid.
When the iron rod is inserted, the magnetic field inside the solenoid is increased. This increases the inductance of the solenoid. So the inductive reactance of the solenoid increases.
Consequently, a large fraction of the applied AC voltage appears across the solenoid. As a result of this, there is a less voltage across the bulb and the brightness of the bulb decreases.