1. Differentiate between electric conductors and insulators. Give two examples in each case?
2. Give reason
(a) A blacksmith heats the metal rim to fix it on a cartwheel.
(b) An electrician use rubber gloves while repairing an electric circuit.
3. What will happen if you join the two terminals of a cell without connecting them through a
switch /a bulb?
4. A black material (tar) is heated for repairing a road. Whether the change caused in tar, by
heating can be reversed?
5. Draw a diagram to show the closed circuit for a switch, bulb and dry cell?
Answers
Answer:
1)Copper, silver, aluminium, mercury are the examples of the conductor. The wood, paper, ceramic etc., are the examples of an insulator. The conductor is used for making electrical wires and cables. The insulator is used for separating the current carrying conductors and for supporting the electrical equipment.
2)A blacksmith heats the metal rim to fix it onto a cart wheel because a metal rim is made slightly smaller. On heating, the rim expands and fits onto the wheel. Then on cooling, the rim contracts and fits tightly onto the wheel.
3)Never join the two terminals of the electric cell without connecting them through a switch and a device like a bulb: Because if you do so, the chemicals in the electric cell get used up very fast and the cell stops working. How do we connect wires to the electric cell?
Explanation: