The electric bell consists of a U-shaped electromagnet. One end of the windings of the electromagnet is connected directly to the negative pole of the battery. The other end of the windings is connected to a make-and-break arrangement and the circuit is completed to the positive pole of the battery through a push-button switch. The make-and-break arrangement consists of a spring-mounted soft-iron strip known as armature A. The armature carries with it a gong and a light spring to which a disc of silver is soldered. The silver disc makes contact with the adjusting screw mounted on a pillar.
When the current in the coils of the electromagnet is switched on by pressing the push button, the armature A is attracted towards the magnet. As soon as the armature moves, it breaks contact with the adjustable contact screw. The current ceases to flow through the coil of the electromagnet, which, therefore, no longer attracts the armature. The armature is pulled back by the spring action until it once again closes the circuit. The entire cycle of make-and-break repeats itself and continues as long as the push button is pressed. Since the armature carries a gong, its to-and-fro motion causes the bell to ring.
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