In an electric bell, the sound is produced when the [[1]] strikes the gong.

An electric bell consists of an electromagnet, switch, iron strip, contact screw, hammer and a gong.

• When the switch is ON, the circuit gets closed and an electric current is passed through the circuit.
• Due to the electric current, the wounded iron coil starts acting as an electromagnet.
• This electromagnet pulls the iron strip.
•  In the process, the hammer at the end of the strip strikes the gong of the bell to produce a sound.

Therefore, 'hammer' is the correct response.