NCERT Solutions: Electricity & Circuits

Q1: Fill in the blanks:
(a) A device that is used to break an electric circuit is called _______________.
(b) An electric cell has _______________ terminals.
Ans:
(a) A device that is used to break an electric circuit is called a switch.
(b) An electric cell has two terminals.

Simple switch

Q2: Mark 'True' or 'False' for the following statements:

(a) Electric current can flow through metals.

Ans: True

Explanation: Metals have freely movable electrons that allow electric current to pass through them easily, so current flows in metals.

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

Ans: False

Explanation: Jute is an insulating material and does not allow electric current to pass, so it cannot be used as a substitute for metal wires in a circuit.

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

Ans: False

Explanation: Thermocol is an insulator and does not conduct electricity, so current cannot pass through it.

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

Ans: The handle of the screw is made of an insulating material, so it does not allow electric current to flow through it. Because the circuit remains open at that point, the bulb does not receive current and therefore does not glow.

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

Ans:

Join one free end of the wire to the metal tip (base) of the bulb and the other free end to the metal screw cap. This completes the circuit so that current can flow and the bulb will glow.

Q5: What is the purpose of using an electric switch? Name some electrical gadgets that have switches built into them.
Ans: An electric switch is used to open or close an electric circuit, allowing us to turn an appliance on or off when needed.
It helps to control the flow of electricity and makes using devices safe and convenient.
Common appliances with built-in switches include lights, fans, televisions, refrigerators and electric irons.

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

Ans: No. An eraser is an insulator and does not conduct electricity, so the circuit would remain open and the bulb would not glow.

Q7: Would the bulb glow in the circuit shown in Fig?

Ans: No. The bulb will not glow because the circuit is incomplete - both terminals of the cell are not connected to both terminals of the bulb

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.
Ans: The object is a conductor.
Explanation: If the conduction tester's bulb glows when the object is connected, it means electric current has passed through the object. This shows that the object allows electric current to flow and therefore is a conductor.

Q9: Why should an electrician use rubber gloves while repairing an electric switch at your home? Explain.
Ans: Rubber is an insulator and does not allow electric current to pass through. When an electrician wears rubber gloves, the gloves prevent electric current from reaching the electrician's body if they accidentally touch a live wire, reducing the risk of electric shock and ensuring safety during repair work.

Rubber gloves for repairing electric switch

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?
Ans: Plastic or rubber covers act as insulators and prevent electric current from passing from the metal part of the tool to the electrician's hand. This reduces the risk of electric shock and makes it safer to work on electrical equipment.