The bell or gong (B), which is often in the shape of a cup or half-sphere, is struck by a spring-loaded arm (A) with a metal ball on the end called a clapper, actuated by an electromagnet (E). In its rest position the clapper is held away from the bell a short distance by its springy arm.

A bell box is an audible device, often electric, which when activated, emits a chime, bell, or buzzer sound.

The electric bell was invented by Alexander Graham Bell, an American scientist. He was born in Edinburg, Scotland on March 3rd, 1847. Electric bells are used in houses, schools and factories. They make use of electromagnets, invented by William Sturgeon in 1823.

When the clapper strikes, the bell begins to move quickly back and forth or vibrate and push the molecules in the air back and forth to form sound 'waves'. Sound needs a medium to travel through, such as air which is made up of molecules that vibrate and conduct the sound.