Question

Give scientific reasons.

(a) The copper wire used in an electro-magnet is insulated.

(b) In an electric bell, the electric current stops again and again.

(c) Electrical switches are made of plastic.

(d) The fuse wire is made of a good conductor.

Answer 1

(a) Insulation of copper wires makes each turn to be separate from other. This is required for the proper functioning of an electro−magnet. If they are not insulated, there is a chance that two turns touch each other causing short circuit and that in turn, can damage the electro−magnet.

(b) When we press the switch, the circuit gets completed and an electric current flows through the coil making the core an electro−magnet. Electro−magnet attracts the flexible iron strip. The striker then hits the gong and a sound is produced. However, in this position, the contact of the strip with the screw breaks and the current in the circuit stops. The coil no more remains magnetic. So, the flexible strip moves back and makes contact with the screw. This cycle is repeated. Hence, the electric current stops again and again in an electric bell.

(c) Electrical switches are used to connect or disconnect the circuit. They are made of plastic, which is an insulating material. The switch is controlled by us and human body is a good conductor of electricity. So, there is no direct contact between human body and electrical circuit. Hence, electrical switches are made of plastic.

(d) The fuse wire is extremely thin. When an excessive current passes through this thin wire, it melts down and breaks the circuit. It prevents damaging the electrical appliances connected through the circuit. Due to this reason fuse is made of good conductor.