An electric bulb is connected in series with a solenoid and they are connected with an AC supply. When a soft iron rod is inserted in solenoid then the intensity of electric bulb will be

CONCEPT:

• An electromagnet is a type of magnet in which the magnetic field is produced by an electric current.
• The magnetic field disappears when the current is turned off.

EXPLANATION:

• When a soft iron core is inserted inside the solenoid then the strength of the magnetic field becomes very large because the iron core gets magnetized by induction.
• The soft iron core helps in concentrating the magnetic lines of forces through the solenoid so that the magnetic field is almost uniform at the end face of the core.
• Hence, the strength of the magnetic field increases when a soft iron core is inserted inside a solenoid.
• 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 less voltage across the bulb and the brightness of the bulb decreases. Therefore, option 2 is correct.

• The strength of an electromagnet can be increased by increasing the number of turns of wire around the iron core and by increasing the current or voltage.