<P> 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 . Electric bells have been widely used at railroad crossings, in telephones, fire and burglar alarms, as school bells, doorbells, and alarms in industrial plants, since the late 1800s, but they are now being widely replaced with electronic sounders . It consists of coils of insulated wire wound round iron rods . When an electric current flows through the coils, the rods became magnetic and attract a piece of iron attached to a clapper . The clapper hits the bell and makes it ring . </P> <P> The most widely used form is the interrupter bell, which produces a continuous sound when current is applied . See animation, above . 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 . When an electric current is enabled to pass through the winding of the electromagnet (via a closing of the switch (K) i.e. pressing the door bell) 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 (T) 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, many times per second, resulting in a continuous ringing . </P>

What do you mean by armature of bell