Electric bell

An electric bell is a mechanical bell that functions by means of an electromagnet. When an electric current is applied, it produces a repetitive buzzing or clanging sound. They were once widely used in fire and burglar alarms, as school bells, doorbells, and alarms in industrial plants, but are now mostly replaced in these applications by electronic buzzers or beepers.

An electric bell is a mechanical bell that functions by means of an electromagnet. When an electric current is applied, it produces a repetitive buzzing or clanging sound. They were once widely used in fire and burglar alarms, as school bells, doorbells, and alarms in industrial plants, but are now mostly replaced in these applications by electronic buzzers or beepers. How it

Electric bell

works

The bell, which is often in the shape of a cup or half-sphere, is struck by a springloaded arm called a clapper, actuated by an electromagnet. In its rest position the clapper is held away from the bell a short distance by its springy arm. When an electric current is passed through the winding of the electromagnet it creates a magnetic field that attracts the iron arm of the clapper, pulling it over to give the bell a tap. This opens a pair of electrical contacts attached to the clapper arm, interrupting the current to the electromagnet. The magnetic field of the electromagnet collapses, and the clapper springs away from the bell. This closes the contacts again, allowing the current to flow to the electromagnet again, so the magnet pulls the clapper over to strike the bell again. This cycle repeats rapidly, perhaps 10 times per second, resulting in a repetitive ringing.