Select the correct option in Questions 1 and 2.
Question 1. Which of the following cannot be charged easily by friction?
(a) A plastic scale
(b) A copper rod
(c) An inflated balloon
(d) A woollen cloth.
Solution 1.
(b) A copper rod
Question 2. When a glass rod is rubbed with a piece of silk cloth the rod
(a) and the cloth both acquire a positive charge.
(b) becomes positively charged while the cloth has a negative charge.
(c) and the cloth both acquire a negative charge.
(d) becomes negatively charged while the cloth has a positive charge.
Solution 2.
(b) becomes positively charged while the cloth has a negative charge.
Question 3. Write T against true and F against false in the following statements.
(a) Like charges attract each other (T/F)
(b) A charged glass rod attracts a charged plastic straw (T/F)
(c) Lightning conductor cannot protect a building from lightning (T/F)
(d) Earthquakes can be predicted in advance (T/F)
Solution 3.
a) Like charges attract each other. False
b) A charged glass rod attracts a charged plastic straw. True
c) Lightning conductors cannot protect a building from lightning. False
d) Earthquakes can be predicted in advance. False
Question 4. Sometimes, a crackling sound is heard while taking off a sweater during winter. Explain.
Solution 4. Woollen sweater gets charged due to friction between the body and the sweater which is why a crackling sound is heard while taking off a sweater during winter.
Question 5. Explain why a charged body loses its charge if we touch it with our hand.
Solution 5. When we touch a charged body, the charges get conducted to the earth through our hands. This process is called electric discharge.
Question 6. Name the scale on which the destructive energy of an earthquake is measured. An earthquake measures 3 on this scale. Would it be recorded by a seismograph? Is it likely to cause much damage?
Solution 6. The scale on which the destructive energy of an earthquake is measured is called the Richter scale. If an earthquake measure 3 on this scale. It Would be recorded by a seismograph. An Earthquake of magnitude 5 or more 5 is considered to be destructive. Hence, an earthquake measured 3 on the Richter scale would not cause much damage.
Question 7. Suggest three measures to protect ourselves from lightning.
Solution 7. Following are the three measures to protect ourselves from lightning:
(i) Always remain indoors. If you are out somewhere try to get inside any building or in car with its door close.
(ii) Do not touch any electrical wires, telephone cables, or metal pipes.
(iii) Do not bathe in running water.
Question 8. Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon.
Solution 8. A charged body always attracts an uncharged body and repels the charged body that is why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon.
Question 9. Describe with the help of a diagram an instrument which can be used to detect a charged body.
Solution 9.
This instrument consists of a metal rod whose one end is fixed to a metallic disc and the other end is fixed with two leaves of aluminium foil. These two leaves of aluminium foil are kept inside a conical flask and a corked fixed on the mouth of the flask to isolate it from the atmospheric air.
When a charged body comes in contact with the metal disc then through conduction the charges reach the aluminium leaves and hence, they move away from each other. In the case of an uncharged body, the aluminium leaves would attract each other.
Question 10. List three states in India where earthquakes are more likely to strike.
Solution 10. The three states in India where earthquakes are more likely to strike are as follows:
- Gujrat
- Assam
- Jammu & Kashmir
Question 11. Suppose you are outside your home and an earthquake strikes. What precaution would you take to protect yourself?
Solution 11. We will take the following precautions to protect ourselves from an earthquake:
- Move to an open area like an open field
- Stay away from any trees, buildings or overhead powerlines that drop to the ground.
- While driving tries to drive slowly and find an open area.
Question 12. The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out on that day. Would you carry an umbrella? Explain.
Solution 12. No, carrying an umbrella during a thunderstorm is not safe because it may conduct charges of the lightning from its metallic rod that may cause an electric shock. Hence, one should not carry an umbrella during a thunderstorm.