NCERT Solutions Class 8 Science Chapter 15: Some Natural Phenomena – Full Exercise Answers

NCERT Solutions Class 8 Science Chapter 15: Some Natural Phenomena

1. Which of the following cannot be charged easily by friction?

Soln: The answer is (b) A copper rod.

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

Soln: The answer is (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.	F
(b) A charged glass rod attracts a charged plastic straw.	T
(c) Lightning conductors cannot protect a building from lightning.	F
(d) Earthquakes can be predicted in advance.	F

4. Sometimes, a crackling sound is heard while taking off a sweater during winter. Explain.

Soln: Rubbing the sweater against the body produces static electricity. The crackling sound is heard when these charges are discharged.

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

Soln: Our body is a conductor. When we touch the object, the charges flow through us into the earth. This is called Earthing.

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?

Soln: The scale is the Richter scale. Yes, it would be recorded by a seismograph, but it is not likely to cause much damage.

7. Suggest three measures to protect ourselves from lightning.

Soln:

• Stay indoors or inside a car with windows closed.
• Avoid bathing or using running water during a storm.
• Stay away from electrical wires and metal objects.

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

Soln: Two charged balloons have the same charge and repel each other. A charged balloon induces an opposite charge on an uncharged balloon, leading to attraction.

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

Soln: An Electroscope is used. It consists of a metal rod with two thin aluminium leaves. When charged, the leaves acquire the same charge and repel each other (open up).

Diagram Labels: Metal Disc, Glass Jar, and Aluminium Leaves.

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

Soln: Gujarat, Assam, and Jammu & Kashmir.

11. Suppose you are outside your home, and an earthquake strikes. What precautions would you take to protect yourself?

Soln:

• Move to an open area away from buildings and trees.
• If in a car, stay inside and drive to a clear spot away from bridges.

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.

Soln: No. Lightning can strike the metal handle of an umbrella and cause a severe electric shock.