15. Some Natural Phenomena Science class 8 in English Medium ncert book solutions Text Book Exercise

Exercise

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.

Answer:

(b) A copper rod.

2. When a glass rod is rubbed with a piece of silk cloth the rod

(a) and the cloth both acquire positive charge.

(b) becomes positively charged while the cloth has a negative charge.

(c) and the cloth both acquire negative charge.

(d) becomes negatively charged while the cloth has a positive charge.

Answer:

(b) becomes positively charged while the cloth has a negative charge.

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 attract 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)

Answer:

(a)-f (b)-t (c)-f (d)-f

4. Sometime, a crackling sound is heard while taking off sweater during winters. Explain.

Answer:

A crackling sound is heard because when the sweater is rubbed while taking it, off, it acuquires a small charge.

5. Explain why a charged body loses its charge if we touch it with our hand.

Answer:

Our body is a conductor of electricity. When we touch a charged body loses charge to the earth through our body.

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?

Answer:

The destructive energy of an earthquakq is measured on a scale called Richter scale. 

An earthquake that meausure 3 on the Richter scale will be recorded by seismograph However, it is not likely to cause much damage.

7. Suggest three measures to protect ourselves from lightning.

Answer:

(i) We should rush to a safer place like house or building.

(ii) 

8. Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?

Answer:

A charged ballon is replled by another ballon beecause both have the same charge. And we know similar charges repel each oother.

Butt a charged ballon attracts an uncharged ballon and lose itts own charge too the other ballon. 

9. Describe with the help of a diagram an instrument which can be used to detect a charged body.

10. List three states in India where earthquakes are more likely to strike.

Answer:

The states that fall in seismic zones are more earthquake-prone. Jammu and Kashmir, Himachal Pradesh, and Gujrat are a few such states.