NCERT Solutions for Class 8 Science Chapter 15 Some Natural Phenomena are part of NCERT Solutions for Class 8 Science. Here we have given NCERT Solutions for Class 8 Science Chapter 15 Some Natural Phenomena.
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NCERT Solutions for Class 8 Science Chapter 15 Some Natural Phenomena
NCERT TEXTBOOK EXERCISES
Select the correct option in Questions 1 and 2.
Which of the following cannot be changed easily by friction?
(a) A plastic scale
(b) copper rod
(c) An inflated balloon
(d) A woolen cloth.
(b) A copper rod.
When a glass rod is rubbed with a piece of silk cloth the rod
(а) 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,
(d) becomes negatively charged while the cloth has a positive charge.
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)
Sometimes, a crackling sound is heard while taking off a sweater during winters. Explain.
The crackling sound is heard because when the sweater is rubbed while taking it off, it acquires a small charge.
Explain why a charged body loses its charge if we touch it with our hand.
When we touch a charged body the total charge is transferred into the earth through our body and it loses its charge.
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?
The destructive energy of an earthquake is measured on a scale called the Richter scale. An earthquake that measures 3 on the Richter scale Will be recorded by a seismograph. However, it is not likely to cause much damage.
Suggest three measures to protect ourselves from lightning.
- We should not use TV or cable phone during lightning.
- After hearing the last thunder, wait for at least 30 minutes before coming out of the safe place.
- A house or a building is a safe place. If you are travelling by car or by bus, you are safe inside with the windows and doors of the vehicle shut.
Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?
A charged balloon is repelled by another charged balloon because both have the same charge. And we know similar charges repel each other. But a charged balloon attracts an uncharged balloon and loses its own charge to the other balloon.
Describe with the help of a diagram an instrument which can be used to detect a charged body.
Electroscope: An electroscope is a device used to detect the presence of charge of an object.
Principle: It works on the principle that like charges repel while unlike charges attract each other.
Structure and Working: An electroscope has a metal rod with a thin metal strip or leaf attached to it at the bottom. At the top, the rod enters into a cup. The bottom part of the rod and leaf is enclosed in a glass box for protection. When the knob of the electroscope is touched with a charged ebonite or glass rod, the leaves open out or diverge. The extent of divergence depends upon the amount of charge on the electroscope.
List three states in India where earthquakes are more likely to strike.
The states that fall in seismic zones are more earthquake-prone. Jammu and Kashmir, Himachal Pradesh, and Gujarat are a few such states.
Suppose you are outside your home and an earthquake strikes. What precautions would you take to protect yourself?
- Find a safe place, that will be away from buildings, trees and overhead power lines. Do not be on the ground but squat low on it to make yourself the smallest target to be struck.
- If we are in a car or a bus, we should not come out, as the driver needs to drive slowly to a clear spot. Do not come out till the earthquake stops.
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.
No, I would not carry an umbrella. Because the pointed rod of the umbrella can become a target of lightning.
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