Are Electromagnets Used in Doorbells?

Electromagnets

• Electromagnets are composed of a metal core wrapped with a coil of wire, called a solenoid. Electric current generates a magnetic field and creates an electromagnet when it passes through the wire. An electromagnet can only exert a magnetic force while electricity flows through the solenoid. Electromagnets turn off when the current is switched off.

Bell Mechanism

• The doorbell button is a switch that opens and closes the circuit. Pushing the button completes the circuit; electric current flows through the solenoid and turns on the electromagnet. The electromagnet attracts, or pulls, a metal striker, which hits a bell to make the doorbell sound. When the button is released, the circuit is interrupted and the electromagnet is turned off. A spring pulls the striker back.

Chime Mechanism

• Other electromagnetic doorbells use a plunger mechanism. A doorbell with a chime unit has an iron plunger with a plastic core. In the "off" position, the plunger is partially inserted in a solenoid. When the button is pushed, the electromagnet is turned on and the electromagnetic force pulls the plunger into the solenoid, which activates the chime unit.

Electronic Doorbells

• Some newer doorbells contain an integrated circuit that activates a digital recording of a chime or other sounds when the doorbell button is pushed.