SCIENCE CHAP 12 ELECTRICITY & CIRCUITS WORKBOOK QUES - ANSWER

                                                         Ch 12. Electricity and Circuits 

1. Choose the correct option. (Ap/U) 

a) Which of the following materials allow an electric current to pass through  them? 

i) Cotton ii) Copper  

iii) Wood iv) Plastic  

Ans: Copper 

b) A dry cell consists of zinc metal that acts as the__________ terminal and a  carbon rod that acts as the ___________ terminal of the cell. 

i) negative, negative ii) positive, negative 

iii) negative, positive iv) negative, negative  Ans: negative, positive 

c) _________ acts as the negative terminal of a bulb. 

i) bottom of the bulb ii) Ammonium chloride iii) metal case iv) Manganese dioxide Ans: metal case 

2. State true or false: (U) 

a) Electricity is a form of energy resulting from the existence of charged  particles. 

Ans: True 

b) We should use water to extinguish a fire in electric wires.  

Ans: False 

c) Electrons do not revolve around the nucleus in fixed orbits. 

False 

3. Give an example for each of the following. (Ap) 

a) Natural resources used to generate electricity 

Ans: Sun, wind, water and nuclear energy

b) Secondary cells 

Ans: Car batteries 

4. In the following questions, two statements are given- one labelled  Assertion (A) and the other labelled Reason (R). Read the statements  carefully and choose the correct alternative (A), (B), (C) and (D) as given  below. (An) 

(A) Both A and R are true and R is the correct explanation of the assertion. (B) Both A and R are true but R is not the correct explanation of the  assertion. 

(C) A is true but R is false. 

(D) A is false but R is true. 

a) Assertion : In an electric bulb, the filament is made up tungsten. Reason: Tungsten does not melt even when the filament glows at a very high  temperature. 

(A) Both A and R are true and R is the correct explanation of the  assertion. 

b) Assertion: If you notice a spark in a switch, put it off immediately with the  help of a metal stick. 

Reason: Metal is a good conductor of electricity. 

(D) A is false but R is true. 

5. Explain the following: (U) 

a) Nucleus  

Ans: Protons and neutrons form the central part of the atom called the  nucleus. 

b) Conductors  

Ans: The materials that allow an electric current to flow through them.  

6. Answer the following questions in brief. (R/U) 

a) What is an electric cell? Name the two types of electric cells. Ans: Electric cell is a device that generates an electric current. It converts  chemical energy into electrical energy. Electric cells are of various shapes  and sizes.  

Primary cell/dry cell and secondary cell/lead-acid accumulators

b) Name the scientist who has discovered electricity. Why is electricity  important?  

Ans: Benjamin Franklin 

All gadgets and devices like computers, televisions, washing machines,  refrigerators, fans, air conditioners, etc. which make our lives  comfortable work on electricity. 

7. State the function of each of the following: (R) 

a) Electric switch  

Ans: An electric switch is used to open or close an electric circuit. 

b) The plastic coating of electric wires 

Ans: Protect us from getting electric shocks. 

8. You are given two dry cells, switch and bulb. Draw an electric torch showing  two dry cells. Which component of the torch is responsible for the flow of  electric current? (C) 

Ans: 

The electric cells inside the torch are responsible for the flow of electric  current. 

9. Observe the picture and answer the questions that follow. (Ap) (a) (b) (c)

In which of the following arrangements will the bulb? Give Reason. (b) 

In (b), the bulb will glow as the circuit is complete. 

10. Aditya performed an experiment to observe the flow of electric current  through an electric bulb. The bulb is connected to the cells in two different  ways as shown in (a) and (b). Which of these is the correct way to connect the  bulb? Why? (U) 

(a) (b)

(b) To complete the circuit and for the flow of current in the electric  circuit, the arrangement of cells are in correct order. 

11. Who am I ? (U) 

1. I am displayed on electric poles and transformers, warning you to stay away  from me. 

Danger sign 

2. I am a continuous flow of electrons 

Electric current 

3. I am round in shape. I provide energy to electronic devices like wrist watches  and pocket calculators. 

Button cell 

12. Higher Order Thinking Skills (HOTS) (U) 

Seema was testing electric circuits. She tested two conditions as given in fig A  and fig B. 

REFER TO TEXTBOOK FOR DRAWING

(a) What will be the direction of flow of current in fig A and fig B? fig A – P to Q 

fig B – Q to P 

(b) In which of the above figures will the bulb glow?  

Both fig A and fig B 

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