NCERT solution for class 8 || Science || Chapter 15 - Some natural phenomena

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NCERT solution for class 8 || Science || Chapter 15 - Some natural phenomena

Chapter 15 Some natural phenomena 

Exercise 

Select the correct option in question 1 and 2 

Q1. Which of the following cannot be charged easily by friction .

a) A plastic scale  

b)A copper rod 

c) An inflated balloon 

d)  A woolen cloth  

Answer- A copper rod 

Q2. When a glass rod is rubbed with a piece of silk cloth the rod 

a)  Cloth both acquire positive charge 

b) Becomes positively charged while the cloth has  negative charge.

c) And the both cloth  acquire negative charge .

d) Becomes negatively charged while the cloth has a positive charge  

Answer-b) Becomes positively charged while the cloth has  negative charge.

Q3. Write T against true and F against false in the following statement 

a) Like charges attract each other 

b) A charged glass rod attract a charged plastic straw 

c) Lightning conductor cannot protect a building from lightening 

d) Earthquake can be predicted in advance .    

Answer- a) false 

b) true 

c) false 

d) false

Q4. Sometimes a crackling sound is heard while taking off a sweater during winters explain?

Answer - Sweater made up of wool and cloth we were inside the sweater it may be made up of mixed fibre when they constantly rubbed on each other then the electrons become free and when some quantity of electron release the accumulated inside the fibres and we take off the sweater they become release in the form of sound and light so we heard the crackling sound

Q5. Explain why A charged body loss its charge if it touch it with our hands? 

Answer -  When we touch to the charged body then the excess amount of accumulated static charge get transferred to ground from our  body and becomes a neutral

Q6. Name the scale on which the destructive energy of an earthquake is measured and earthquake measures the tree on a scale would it be recorded by the seismograph ? Is it likely to cause much damage?

Answer - The scale is used to measure the earthquake is called the Richter scale and the reading of the richer scale is measure by seismograph

Q7. Suggest three measures to protect ourselves from lightning? 

Answer-  

  • Stay inside the home or under covered area 
  • Don't use electronic appliances during lightning 
  • Don't use swimming pool during lightning

Q8. Explain why a charged balloon is repelled by another charged balloon there as an uncharged balloon is attracted by another charged balloon ?

Answer- When charged balloon repelled another charged balloon because both contain the same charges and similar charges repel to each other.

But it can attract to an charged balloon because uncharged balloon have opposite charge and opposite charge attract to each other

Q9. Describe with the help of a diagram and instrument which can be used to detect a charged body ? 

Answer - Scope is used to measure the body is charged and uncharged 

In electroscope a metal strip is fix in a glass container with the help of conductor two metal foil are attached to it  .When the charged body is attached to the metal rod if the charges are like then the metal foils are repel to each other in this way we can detect the charged body.

Q10. List three states in India where earthquake are more likely to strike? 

Answer - Three state in India where earthquake are more likely to strike are Assam Gujarat and Jammu Kashmir

Q11. Suppose you are outside your home and an earthquake strikes what precaution would you take to protect yourself? 

Answer-  Some precautions are to take protect our self 

  • Suddenly move to the open space 
  • If you are in bus or car then don't come outside 
  • Don't take a shelter under the trees buildings and overhead electricity lines   

Q12. The weather department has predicted that the thunderstorm is likely to occur on a certain day suppose you have to go out on that day would be you carry an umbrella explain? 

Answer - No we should not carry the umbrella because it is more risky because during thunderstorm The lightening is also occurs and in lightening the free charges are release and maybe these charges are acquired by the metal rod of umbrella and it create the electric shock




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