Question

what type of magnet is used in an electric bill explained and draw a labelled diagram of an( electric bell it is a 10 mark questions)

Answer 1

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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

How it works

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.

The tone of the sound generated depends on the shape and size of the bell or gong resonator. Where several bells are installed together, they may be given distinctive rings by using different size or shapes of gong, even though the strike mechanisms are identical.

Another type, the single-stroke bell, has no interrupting contacts. The hammer strikes the gong once each time the circuit is closed. These are used to signal brief notifications, such as a shop door opening for a customer, rather than continuous warnings.

Answer 2

An electro magnet is used in an electric bell.
the electric bell has a soft iron rod that is attached to a hammer at one end. when this hammer hits a metal disc called a gong,it makes a sound. the iron rod is mounted on a spring and is placed near an electromagnet. the circuit has a switch,which controls the flow of electricity.
when the switch is turned on, current flows through the electro magnet. the electromagnet attracts the soft iron rod towards itself. this causes the hammer that is attached to the rod to hit the gong and produce ringing sound.
the movement of the iron rod towards the electro magnet breaks the circuit. the electro magnet loses its magnetic nature since current does not flow through it; it can thus no longer attract the iron rod. the iron rod moves bact to its original position and completes the circuit ones more. the electromagnet regains its magnetic nature. the hammer hits the gong again. this process of completing and breaking the circuit goes on and the bell rings as long as the switch is on.