Q1. Fill in the blanks:

(a) A device that is used to break an electric circuit is called _______________.

Answer: switch

(b) An electric cell has _______________ terminals.

Answer: two

Q2. Mark ‘True’ or ‘False’ for following statements:

(a) Electric current can flow through metals.

Answer: True

(b) Instead of metal wires, a jute string can be used to make a circuit.

Answer: False

(c) Electric current can pass through a sheet of thermocol.

Answer: False

Q3. Explain why the bulb would not glow in the arrangement shown in Fig. 12.13.

Answer: Bulb would not glow in the arrangement because insulator is present in this circuit, hence the circuit is not complete.

Q4. Complete the drawing shown in Fig 12.14 to indicate where the free ends of the two wires should be joined to make the bulb glow.

Answer:

Q5. What is the purpose of using an electric switch? Name some electrical gadgets that have switches built into them.

Answer: Electric switch is used in the electric circuit to complete and break the circuit.

Some electric gadgets that have switches built into them i.e. refrigerator, fan, bulb etc.

Q6. Would the bulb glow after completing the circuit shown in Fig. 12.14 if instead of safety pin we use an eraser?

Answer: No, bulb will not glow because eraser is an insulator.

Q7. Would the bulb glow in the circuit shown in Fig. 12.15?

Answer: No, the bulb will not glow because there is not the proper connection across the bulb terminal.

Q8. Using the “conduction tester” on an object it was found that the bulb begins to glow. Is that object a conductor or an insulator? Explain.

Answer: The object is a conductor because the bulb will glow only when the conductor is used. If we use insulator there, the bulb will not glow.

Q9. Why should an electrician use rubber gloves while repairing an electric switch at your home? Explain.

Answer: An electrician uses rubber gloves while repairing an electric switch at home because rubber is an insulator. It does not allow to pass electricity through it. It protects the electrician from electric shocks.

Q10. The handles of the tools like screwdrivers and pliers used by electricians for repair work usually have plastic or rubber covers on them. Can you explain why?

Answer: Tools like screwdrivers and pliers used by electricians for repairing works usually have plastic or rubber covers on them at their handle. Plastics or rubbers are insulators. Insulators do not allow to pass an electric current through them. They protect electrician from electric shocks.