CBSE Class 8 Science Some Natural Phenomena VBQs

Question. Which of the following cannot be changed easily by friction?
(a) A plastic scale
(b) A copper rod
(c) An inflated balloon
(d) A woollen cloth
Answer : B

Question. 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
Answer : B

Write T against true and F against false in the following statements.

(a) Like charges attract each other.
Answer : False

(b) A charged glass rod attracts a charged plastic straw.
Answer : True

(c) Lightning conductor cannot protect a building from lightning.
Answer : False

(d) Earthquakes can be predicted in advance.
Answer : False

Question. 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 with our hand, the charged body loses charge to the earth through our body.

Question. Describe with the help of a diagram an instrument which can be used to detect a charged body.
Answer : Electroscope is a device which is used to detect the charge on a body. It works on the principle that like charges repel each other while unlike charges attract each other. It consists of a metal rod with thin metal strip or leaf attached to it at the bottom.

Question. Sometimes, a crackling sound is heard while taking off a sweater during winters. Explain.
Answer : When we take out sweater, Woolen sweater gets charged due to friction between the sweater and the body. This results in crackling sound.

Question. List three states in India where earthquakes are more likely to strike.
Answer : Kashmir, Rajasthan and Gujarat.

Question. 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 earthquake is measured on a scale called Richter scale. It has reading from 1 to 10. Earthquake with more than 7 values can cause much damage.
An earthquake measure 3 on this scale will be recorded by a seismograph. But it is not likely to cause much damage.

Question. Suppose you are outside your home and an earthquake strikes. What precaution would you take to protect yourself?
Answer : (i) Move to open space. Find a clean spot away from buildings, trees and overhead power lines. Drop to the ground.
(ii) If we are in a car or a bus, will not come out. Drive slowly to a clear spot and remain in it till the earthquake stops.

Question. Suggest three measures to protect ourselves from lightning.
Answer : (i) Do not use TV or cable phone during lightning.
(ii) Stay indoors or under covered area.
(iii) Don’t take bath during lightning.

Question. 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.
Answer : No, it is not advisable to carry

Question. Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?
Answer : We know that same charges repel and opposite charges attract each other. A charged balloon is repelled by another charged balloon because both carry same type of charges. On the other hand, an uncharged balloon is attracted by another charged balloon as they have opposite charges.