NCERT-6 Science Solutions
Chapter 12: Electricity and Circuits
NCERT TEXTBOOK EXERCISES-Pages 123-124
Question 1. Fill up the blanks:
(a) A device that is used to break an electric circuit is called _______.
(b) An electric cell has _______ terminals.
Question 2. Mark ‘True’ or ‘False’ for the following statements:
(a) Electric current can flow through metals.
(b) Instead of metal wires, a jute string can be used to make a circuit.
(c) Electric current can pass through a sheet of thermocol.
Question 3. Explain why the bulb would not glow in the arrangement shown in Fig. 12.7.
The bulb does not light up in the arrangement because the circuit is not complete.
Question 4. Complete the drawing shown in Fig. 12.4 to indicate where the free ends of the two wires should be joined to make the bulb glow.
Question 5. What is the purpose of using an electric switch? Name some electrical gadgets that have switches built into them.
Electric switches are used to stop or start the flow of current. Electric gadgets having switches built into them are heaters, geysers, televisions, mixi, electric bells, fans, cooler, air conditioners, microwave ovens, etc.
Question 6. Would the bulb glow after completing the circuit shown in Fig. 12.8, if instead of a safety pin we use an eraser?
Yes, the bulb will light up after completing the circuit. No, the bulb will not glow if we use an eraser instead of safety pins.
Would the bulb glow in the circuit shown in Fig 12.9?
In this circuit, the bulb is connected through a woollen thread with the negative terminal of the electrical cell. Since the woollen thread is not a conductor of electricity, it will not allow the electricity to flow through it that is from bulb to electrical cell. Thus, the circuit remains incomplete and hence the bulb will not light up.
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.
The material of that object is a conductor as the bulb light up. It means that circuit is complete.
Why should an electrician use rubber gloves while repairing an electric switch at your home? Explain.
While carrying out electrical repairs one must wear rubber gloves. This is because our body is a good conductor of electricity, and if there is any contact of naked wire with our naked hand it will be very dangerous. And if we are with rubber gloves on our hands, the rubber being an insulator will protect us from electric shock.
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?
Wood or plastic are insulators and do not allow electricity to pass through them. Hence electricians must use screwdrivers, with wooden or plastic handles, when they carry out repairs to avoid electric shocks.