CHAPTER 15
SOME NATURAL PHENOMENA
Here is the answer of chapter 15 SOME NATURAL PHENOMENA of NCERT science of class 8.The complete solution of CHAPTER 15 SOME NATURAL PHENOMENA is given here which is prepared subject expert. Some important extra questions and important points about Chapter 15 are also given.
Select the correct option in Questions 1 and 2.
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
Ques 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.
Ques 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) Earthquake can be predicted in advance.(T/F)
Ans.a) False
b) True
c) False
d) False
Ques 4. Sometimes a cracking sound is heard while taking off a sweater during winters.Explain.
Ans. The sweater get changed due to friction while taking the sweater off. These charges get discharged producing cracking sound.
Ques 5. Explain why charged body loses its charge. If we touches it with our hand.
Ans. The human body is a conductor. So when we touch a charged body. The charge passes through our body to the ground and the body looses its charge.
Ques 6. Name the scale on which the destructive energy of an earthquake is measured. An earthquake measures 3 on its scale. Would it be recorded by a seismograph? It is likely to cause much damage?
Ans. The destructive energy of an earthquake is measured on the Richter scale. An earthquake measuring 3 on this scale can be recorded by a seismograph. It does not cause much damage.
Ques 7. Suggest three measures to protect ourselves from lightning.
Ans. I) Lighting conductors should used to protect buildings.
II) Do not take bath under running tap water when there is a chance of lightning to occur.
III) Do not stand under trees when there is a chance of lightning to occur.
Ques 8. Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another
charged balloon?
Ans. When a charged balloon is placed near another charged balloon. They repel each other due to the like charges present on them. However,a charged balloon will attract an uncharged balloon because it include an unlike charge on the near surface of the uncharged balloon.
Ques 9. Describe with the help of a diagram an instrument which can be used to detect a charged body.
Ans. When a charged body is placed in contact with the metal sphere of the electroscope, it gets charged due to conduction. The leaves of the metal foil develop like charges and they diverges. The divergence of the leaves of the metal foil shows that the body put in contact with the sphere of the electroscope is charged if there is no divergence then the body is not charged.
Ques 10. List three states in India where earthquake are more likely to strike?
Ans. In India, earthquake are most likely to strike in Gujarat, Assam and Kashmir.
Ques 11. Suppose you are outside your home and an earthquake strikes. What precautions would you take to protect yourself.
Ans. When outside the home,find a clear spot free from buildings,trees and power lines drop down to the ground.
If you are in a car, do not come out of it,slowly drive it to a safe place.
Ques 12. The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out that day. Would you carry an umbrella? Explain.
Ans. The umbrella has a metallic rod with a sharp point if there is lighting it would be dangerous to move under the umbrella. I would not carry an umbrella when going out the day on which the weather department has predicted
a thunderstorm.
This is the complete solution of CHAPTER 15 SOME NATURAL PHENOMENA. This is according to latest syllabus of CBSE 2020-21.
Here's some important points about the CHAPTER 15 SOME NATURAL PHENOMENA of class 8 Science NCERT.
IMPORTANT POINTS:-
a) Electroscope:- An instrument used to detect electrical charge on a body.
b) Lightening:- A high energy Spark produced in the sky accompained by a large amount of heat and light.
c)Lightening conductor:- A metallic conductor fixed on high rise building to protect them from lightening by conducting the atmospheric electricity into the earth.
d)Thunder:- A loud sound produced due to the rapid expansion of air caused by heat produce during lightening.
e) Earthing:- The process of discharging atmospheric electricity through a metallic conductor into the earth is called Earthing.
f) Earthquake:- An earthquake is sudden shaking or trembling of earth which lasts for a very short time.
g)Richter Scale:- A scale on which power of earthquake is measured in terms of magnitude.
h) Seismograph:- An instrument which is used to record seismic waves which produces tremors on the surface of the earth.
These are some important points of Chap 15.
Here's is some extra Questions about the Chapter 15 SOME NATURAL PHENOMENON of NCERT SCIENCE CLASS 8.
Extra Questions:-
Ques 1. Why does tiny bits of paper attracts towards a comb when rubber against your dry hairs?
Ans. Because when the comb is rubbed against dry hairs then it gets electrically charged and when it brings near to tiny bits of paper it attracts the tiny bits of paper.
Ques 2. Write two damaging effect of lightening.
Ans.a) When lightening strikes a building or tree it can set them on fire.
b) Lightening can cause death of living beings.
Ques 3. How does Lightening take place between the clouds?
Ans. Due to condensation the clouds are formed. When two clouds of positive and negative static charges approach each other a electric charges flows from one cloud to another an intense sparks of electricity is seen in the sky such an electric spark is known as electric discharge of lightning.
Ques 4.How does Lightening conductor prevent damage to building during lightening?
Ans. When highly charged clouds passes over a tall building it induces an opposite charge on the lightening conductor. This charge quickly flow to the earth through the copper strip thus the lightening discharge is prevented as the builder is saved from damage.
Ques 5. What causes an earthquake?
Ans. Earthquake are caused due to the movement in tectonic plates deep inside the earth crust. Tremors on the earth can also be caused when volcanic erupt or an underground nuclear explosion.
Ques 6. What are seismic or fault zone?
Ans. Since, earth quake are caused by the movement of plates the boundary of the plates are the weak zone.Where earthquake are more likely to come these weak zones are also known as Seismic or fault zone.
Ques 7. Write five steps to protect yourself from earthquake.
Ans. a)Take shelter under a table and stay there till the shaking stops.
b) Stay away from tall and heavy objects that may fall on you.
c) If you are on bed do not get up. Protect your head with pillow.
d) Find a clear spot, away from building trees and overhead power lines. Drop to the ground.
e) If you are in a car or a bus, do not come out. Ask driver to drive slowly.
Ques 8. Write any three measures to make a 'quake safe building'.
Ans. a) Consult qualified architect and structural engineer.
b) It is better if the cupboards and shelves are fixed to the walls,so that they do not fall easily.
c)Be careful where you hang wall clocks, photo frames, water heater etc. So that in the event of an earthquake, they do not fall on people.
These are some extra Questions of Chapter 15 SOME NATURAL PHENOMENA of class 8 Science NCERT.
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