NCERT Solutions for Class 8th Science

Chapter 15 – SOME NATURAL PHENOMENA

(Complete Downloadable Chapter Solution PDF file is at the bottom of the page)

 

           Select the correct option in Questions 1 and 2.

Q.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.

Ans    (b) A copper rod

Q.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.

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

Q.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)

Ans    (a) Like charges attract each other (F)

           Correct: Like charges repel each other and unlike charges attract each other.

           (b) A charged glass rod attract a charged plastic straw (T)

           (c) Lightning conductor cannot protect a building from lightning (F)

           Correct: Lightning conductor protects a building from lightning by transferring the charge from the                      building to earth.

           (d) Earthquakes can be predicted in advance (F)

           Correct: Earthquakes cannot be predicted in advance.

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

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

Q.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?

Ans     Destructive energy of an earthquake is measured on Richter scale. An earthquake measures 3 on richter                scale will be recorded by a seismograph. Since its magnitude is small it will not cause much damage.

Q.7      Suggest three measures to protect ourselves from lightning.

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

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

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

Ans    Jammu & Kashmir, Gujarat and Assam.

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

Q.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.