Monday 28 December 2020

Chapter 12 Electricity And Circuits



Chapter 12 – electricity and circuit


ACTIVITY-1: To observe the filament of bulb and its functions.


Question 1- The part of bulb which produces light is called _________.

Answer- Filament.


Question 2- The electric bulb has _______ terminals.

Answer- Two.


ACTIVITY- 3: To make a switch.

Question 1- What is the function of electric switch?

Answer- Electric switch is used to start (ON) or stop (OFF) the flow of electric current in a circuit.



Question 2- In an electric circuit the circuit break when switch is in _______ position.

Answer- OFF.




Question 1- Fill In The Blanks.



a). A device that is used to break or make an electric circuit is called switch.

b). An electric bulb glows when electric current flows through it.

c). Conductors are materials through which electric current can pass.

d). Current cannot pass through insulators.


Question 2- Write True Or False.


a). Electric current can flow through metals. (True)

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

c). Electric current can pass through a pencil lead. (True)

d). When chemicals in dry cell are used up, it stops working. (True)

e). LED based lamps are eco-friendly. (True)


Question 3- Match The Column:-

1. Button cell



2. Dry cell



3. LED bulb.



4. Electric switch





Question 4. Choose The Correct Answer.


(i). Battery is a combination of:

a) Conductors

b) Insulators

c) Electric cells ()

d) Filaments


(ii). The basic electric circuit needs to have:

a) Only a source of electric current

b) Only a few conducting wires

c) Only a device or appliance

d) All the above ()


(iii). On passing current through an electric bulb, bulb starts emitting light because its:

a) Filament starts emitting light and then gets heated up

b) Thick connecting wires start emitting light and then get heated up

c) Filament gets heated up and then starts emitting light ()

d) Thick wires get heated up and then starts emitting light


Question 5- Very Short Answer Type Questions.


(i) What is electric cell?

Answer- Electric cell is a source of electric current.


(ii) What is electric current?

Answer- Electric current is the rate of flow of electric charge in a conductor.


(iii) What is electric circuit?

Answer- Electric circuit is an arrangement of battery, switch, electric device and conducting wires, which provides a complete path for electricity to pass.


Question 6- Short Answer Type Questions.


(i) Tools like screw drivers and pliers used by electricians have handles made up of plastic, rubber, wood. Why?

Answer- Because plastic and rubber are insulators. So it protects the electrician from the shock of electricity.


(ii) Why should we dry our hands before touching an electric appliance or a switch?

Answer- Because normal water is conductor of electricity, so with wet hands we can get electric shock.


(iii) A student while performing an experiment in the science lab, connected an electric bulb to an electric cell through an electric switch. He noticed that the bulb does not glow when the electric switch was set in its ON position. Mention ant two reasons for this observation.

Answer- (1) Electric switch may be faulty,

(2) Connections may be loose,

(3) Electric cell may be used up.


(iv) Distinguish between the terms conductors and insulators of electricity. Give two examples of each type.





1. Conductors are materials through which electric current can pass.


1. Insulators are materials through which electric current cannot pass.


2. Examples: Metals- Iron, copper, aluminium etc.

2. Examples: All non-metals except graphite, rubber, plastic, wood etc.




(v) Explain why the bulb would not glow in the arrangement shown at below:

Answer- Bulb will not glow in the arrangement because the handle of the tester used in the connection is made of plastic which is an insulator.


(vi) Match the labels with the correct parts of the circuit given below:


 Provides Electric Current

A Device used for Making/ Breaking a Circuit

 Device which Lights up






Question 7- Long Answer Type Questions.


(i) Using the “conduction testes” on an object it was found that the bulb begins to glow. Is that object conductor or insulator? Explain.

Answer- That object is conductor, because conductors allow to pass electricity through it. So circuit gets completed and bulb glows.


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

Answer- Because plastic and rubber are insulators. So it protects the electrician from the shock of electricity.