An electric bell is a mechanical bell that works on electromagnet. When the current is passed through it, produces sound like buzzing. It is used in fire or burglar alarms, school bells and door bells etc. But now a day, they are replaced with electronic buzzer.
Bell is often in the shape of a cup or half sphere. It is struck by a spring loaded arm with a metal ball on the end called a clapper, and it actuated by an electromagnet.
When it is in rest position the clapper is held away from the bell with a small distance by its arm.
Magnetic circuit is connected with battery through switch, which is for operation.
Working of Electric Bell
When closing the switch of electric bell, an electric current is passed through the coil of an electromagnet. It makes a magnetic field that attracts the iron arm of the clapper to pull it over to tap a bell.
At that time when arm pull, this opens a pair of electrical contacts attached to the clapper arm and interrupting the current to the electromagnet. Then electromagnet demagnetized and the clapper releases away from the bell. This closes the contacts again.
When allowing the current to flow through electromagnetic circuit again, so the magnet pulls the clapper over to strike the bell again.
This operation can repeats several time per second resulting in continuous ringing.
The type of the sound generated depends on the shape and size of the bell. By connecting different size and shape of bell, obtained different type of sounds.
Type of Electric bells
As per the operating time different type of Electric bells are classified as follows.
This interrupter bell produces continuous sound when the current is passed through its magnetic circuit.
Single stroke Type
Another type of bell is called single stroke bell, it has no interrupting contacts. The hammer strikes the bell once each time when the circuit is closed. These are generally used in shops, signal etc.
In this bell, when the current is passed to an electromagnet, it pulls the clapper against the bell.
A simple development of the single stroke electric bell is the sprung bell. It is used for servant call bells in large houses. The inertia of the heavy bell on the light spring would continue ringing for some seconds after the single stroke.
MCQ Question PDF of Module 12: Domestic Appliances.
- Concept of Neutral and Earth – Cooking range.
- Electric Bell and Buzzer.
- Heating element, heater/immersion heater, electric stove and hot plate.
- Food mixer.
MCQ Question PDF of Domestic Appliances