Electricity and Circuit

NCERT Solution

Fill in the blanks:

  1. A device that is used to break an electric circuit is called ………………….

    Answer: Electric switch
  2. An electric cell has ………….terminals.

    Answer: Two

Mark ‘True’ or ‘false’ for following statements:

  1. Electric current can flow through metals.

    Answer: True
  2. Instead of metal wires, a jute string can be used to make circuit.

    Answer: False
  3. Electric current can pass through a sheet of thermo col.

    Answer: False

Answer the following questions

Explain why the bulb would not glow in the arrangement shown in the given figure?

electric circuit

Answer: The following reasons are possible:

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

electric circuit


electric circuit
Answer the following questions

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

Answer: An electric switch helps us in making or breaking the electric circuit as and when required. It helps in saving electricity and in prolonging the life of an electric cell. Table fan, transistor, mixer-grinder, television, etc. are some gadgets which have inbuilt electrical switches.

Would the bulb glow after completing the circuit in figure (question 4) if instead of safety pin we use an eraser?

Answer: If an eraser is used instead of a safety pin to complete the circuit, the bulb would not glow. Eraser is an insulator and hence it would not allow electric circuit to become complete.

Would the bulb glow in circuit shown in the given figure?

electric circuit

Answer: No, because both the wires are attached to the negative pole of the bulb.

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

Answer: The object is a conductor which is proved by electric circuit becoming complete.

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

Answer: Rubber is an insulator and thus does not allow electric current to pass through it. When an electrician repairs an electric switch, he may get electric shock because leakage in electric current. Rubber gloves prevent him from getting electric shock. Hence, an electrician wears rubber gloves while repairing something.

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: Plastic is an insulator. The plastic handles on screwdrivers and pliers; used by electricians; help in preventing accidental electric shock.

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