Some Natural Phenomena Class 8 Science Chapter 15 Extra Questions and Answers are provided here. We prepared these extra questions based on the latest NCERT Class 8 Science Book. CBSE Class 8 Science Chapter 15 Some Natural Phenomena Extra Questions will help you to properly understand a particular concept of the chapter.

Class 8 Science Chapter 15 Some Natural Phenomena Extra Questions

Very Short Answer Type Question

Question 1: List three states in India where earthquakes are more likely to strike.

Answer: Gujarat, Kashmir, Rajasthan

Question 2: How will you charge a glass rod by the method of friction?

Answer: A glass rod can be charged by rubbing it with silk cloth.

Question 3: What are the two kinds of electric charges?

Answer: There are two kinds of charges — positive charge and negative charge.

Question 4: What is a flash of light which occurs in the sky during the rainy season called?

Answer: Lightning

Question 5: How a ballpoint pen refill can be charged by the method of friction?

Answer: A ballpoint pen refill can be charged by rubbing it against the woolen cloth.

Answer: When two like charges are brought together then they will repel each other.

Question 8: What is the purpose of the Richter scale?

Answer: The Richter scale is used to measure the magnitude (or intensity) of an earthquake.

Question 9: What is directly below the epicenter of an earthquake?

Answer: Focus of an earthquake is located below the epicenter of an earthquake.

Question 10: What kind of electric charge is acquired by a plastic comb rubbed with dry hair?

Answer: The plastic comb acquires negative charge when it is rubbed with dry hair.

Question 11: How an inflated rubber balloon can be charged by the method of friction?

Answer: An inflated balloon can be charged by rubbing it against the woolen cloth.

Question 12: What is focus of an earthquake?

Answer: The place inside the earth’s crust where the earthquake begins is called focus of an earthquake.

Question 13: What is the instrument used to measure and record an earthquake?

Answer: Seismograph is the instrument which is used to measure and record an earthquake.

Question 14: What is epicentre of an earthquake?

Answer: The point on the earth’s surface directly above the focus is called epicentre of an earthquake.

Question 15: What type of electric charge is acquired by a rubber balloon when rubbed with a woolen cloth?

Answer: When balloon is rubbed with a woolen cloth, it acquires negative electric charge.

Question 16: What are seismic waves?

Answer: The tremors produce waves on the surface of the earth. These are called seismic waves.

Question 17: Which device is used to protect buildings from the effect of lightning?

Answer: Lightning Conductor is a device used to protect buildings from the effect of lightning.

Question 18: What is an earthquake?

Answer: An earthquake is a sudden shaking or trembling of the earth lasting for a very short time.

Question 19: What causes them to happen?

Answer: Earthquake is caused by a disturbance deep inside the earth’s crust.

Question 20: Name the scientist who showed that lightning and the spark from your clothes are essentially the same phenomena.

Answer: In 1752 Benjamin Franklin, an American scientist, showed that lightning and the spark from your clothes are essentially the same phenomena.

Short Answer Type Questions

Question 1: If scientists know so much about earthquakes, can they also predict when and where the next one will strike?

Answer: Although, we know for sure what causes an earthquake, it is not yet possible to predict when and where the next earthquake might occur.

Question 2: Other than earthquakes what causes tremors on the earth?

Answer: Tremors on the earth can also be caused when a volcano erupts, or a meteor hits the earth, or an underground nuclear explosion is carried out.

Question 3: A positively charged object attracts another charged object placed near it. What is the nature of charge on the other object?

Answer: The nature of charge on the other object will be negative. This is because like charges repel each other and unlike charges attract each other.

Question 4: Explain why a charged body loses its charge if we touch it with our hand.

Answer: When we touch a charged body with our hand, then the electric charge present on it flows to the earth through our hand and body. That is why a charged body loses its charge if we touch it with our hand.

Question 5: What was the magnitude of Bhuj and Kashmir earthquakes on the Richter scale?

Answer: Really destructive earthquakes have magnitudes higher than 7 on the Richter scale. Both Bhuj and Kashmir earthquakes had magnitudes greater than 7.5.

Question 6: Why does a plastic comb rubbed with dry hair attract tiny pieces of paper?

Answer: When a plastic comb is rubbed with dry hair, it acquires a small charge due to friction. The electrically charged comb then exerts an electric force on the tiny pieces of paper and attracts them.

Question 7:  Why is it not safe to stay under a tree during a thunderstorm?

Answer: During a thunderstorm, there is danger of lightning striking the tree and burning it up. This lightning can also pass through the body of the person standing under the tree and may kill him. Therefore, it is not wise to stand under a tree during a thunderstorm.

Question 8: When a charged refill is touched with the metal top of an electroscope, its aluminium leaves diverge. Give reason.

Answer: The aluminium foil strips receive the same charge from the charged refill through the paper clip. The strips carrying similar charges repel each other and they become wide open.

Question 9: What happens when plates brush past one another, or a plate goes under another due to collision?

Answer: When plates brush past one another, or a plate goes under another due to collision, they cause disturbance in the earth’s crust. It is this disturbance that shows up as an earthquake on the surface of the earth.

Question 10: 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: Carrying umbrella is not a good idea at all during thunderstorms because lightning may strike the top end of the metal rod of umbrella and harm us.

Question 11: Sometime, a crackling sound is heard while taking off sweater during winters. Explain.

Answer: When we take off a woolen (or synthetic) sweater, it rubs against our shirt. Due to rubbing, opposite electric charges develop on them, which attract each other. The discharge of these electric charges produces tiny sparks of light as well as crackling sound.

Question 12:  What will happen when the metal top of an electroscope is touched with a glass rod which has been rubbed with silk cloth? Give reason for your answer.

Answer: The aluminium foil strips receive the same charge from the charged glass rod through the paper clip. The strips carrying similar charges repel each other and they become wide open.

Question 13: What happens when you touch the paper clip of a self-made Electroscope? Why does it happen? What is this process called?

Answer: Every time the foil strips collapse as soon as we touch the paperclip with hand. The reason is that the foil strips lose charge to the earth through our body. The process of transferring of charge from a charged object to the earth is called earthing.

Long Answer Type Questions

Question 1:  What damage is caused by lightning?

Answer: When lightning strikes a tree, it can burn up the tree. And when a person is hit by lightning during a thunderstorm, then electric energy passes through the body of the person due to which the person get severe burns and get killed. Thus, it can cause a lot of destruction by damaging property, trees and killing people.

Question 2:  How can we determine if an object is charged or not?

Answer: An electroscope may be used to detect whether a body is charged or not. When the object is touched with the metal cap of an electroscope, both the metal cap and the leaves acquire the same charge from the charged object through the paper clip. It will cause the leaves to diverge showing that the object was charged.

Question 3:  What is lightning conductor? How does it work?
Or
How does a lightning conductor protect a tall building?

Answer: Lightning Conductor is a device used to protect buildings from the effect of lightning. A metallic rod, taller than the building, is installed in the walls of the building during its construction. One end of the rod is kept out in the air and the other is buried deep in the ground. The rod provides easy route for the transfer of electric charge to the ground.

Question 4:  What are the various effects of an earthquake?

Answer: The various effects of an earthquake are:

• They can cause immense damage to buildings, bridges, dams and people. There can be a great loss to life and property.
• The earthquakes can cause floods, landslides and tsunamis.
• A major tsunami occurred in the Indian Ocean on 26th December 2004. All the coastal areas around the ocean suffered huge losses.

Question 5: What will you do to protect yourself from lightning if you are in an open field?

Answer: If no shelter is available and we are in an open field, we should stay far away from all trees. We should stay away from poles or other metal objects. We should not lie on the ground instead we should squat low on the ground. We should place our hands on our knees with our head between the hands. This position will make us the smallest target to be struck.

Question 6: Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?

Answer: A charged balloon is repelled by another charged balloon because both the balloons have same type of charges and like charges repel each other. Whereas an uncharged balloon is attracted by another charged balloon because charged balloon induces opposite charges in the nearer end of the uncharged balloon by electric induction and unlike charges attract each other.

Question 7: Suppose you are outside your home and an earthquake strikes. What precaution would you take to protect yourself?

Answer: If we are outside our home and an earthquake strikes, then

• We should try to find a clear spot, away from buildings, trees and overhead power lines. Drop to the ground.
• If we are in a car or a bus, we should not come out. We should ask the driver to drive slowly to a clear spot. We should not come out till the tremors stop.

Question 8: 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 by Richter scale. An earthquake of 3 Richter can be recorded by a seismograph. An earthquake of magnitude 3 on Richter scale is often felt but not likely to cause much damage. Really destructive earthquakes have magnitudes higher than 7 on the Richter scale.

Question 9: What precautions would you take to protect yourself during an earthquake if you are at home?

Answer: In order to protect ourselves during an earthquake we must take following precautions:

• We should take shelter under a table and stay there till shaking stops.
• We should stay away from tall and heavy objects that may fall on us.
• If we are in bed then we should not get up and should protect our head with a pillow.

Question 10: Suggest three measures to protect ourselves from lightning.

Answer: Measures to protect ourselves from lightning

• A house or a building is a safe place. If we are travelling by car or by bus, we are safe inside with windows and doors of the vehicle shut.
• Lightning can strike telephone cords, electrical wires and metal pipes.      During a thunderstorm when lightning is taking place, contact with these should be avoided.
• Carrying umbrella is not a good idea at all during lighting because lightning may strike the top end of the metal rod of umbrella and harm us.

Question 11: What causes an earthquake?

Answer: Causes of an earthquake

• The outermost layer of the earth is not in one piece. It is fragmented. Each fragment is called a plate. These plates are in continual motion. When they brush past one another, or a plate goes under another due to collision, they cause disturbance in the earth’s crust. It is this disturbance that shows up as an earthquake on the surface of the earth.
• Tremors on the earth can also be caused when a volcano erupts, or a meteor hits the earth, or an underground nuclear explosion is carried out.

Question 12: What causes lightning in the sky?

Answer: During the development of a thunderstorm, the air currents move upward while the water droplets move downward. These vigorous movements cause separation of charges. The positive charges collect near the upper edges of the clouds and the negative charges accumulate near the lower edges. There is accumulation of positive charges near the ground also. When the magnitude of the accumulated charges becomes very large, the air which is normally a poor conductor of electricity is no longer able to resist their flow. Negative and positive charges meet, producing streaks of bright light and sound. We see streaks as lightning. The process is called an electric discharge.

Question 13: State some precautions that people should take to protect themselves against earthquakes if they live in seismic zones of the country.

Answer: People living in seismic zones should take the following measures for protection against earthquakes:

• All the buildings in these zones should be designed so that they can withstand major tremors. Modern building technology can make it possible.
• In highly seismic areas, the use of mud or timber is better than the heavy construction material. Keep roofs as light as possible. In case the structure falls, the damage will not be heavy.
• It is better if the cupboards and shelves are fixed to the walls, so that they do not fall easily.
• Wall clocks, photo-frames, water heaters etc., should be mounted securely on the walls, so that in the event of an earthquake, they do not fall on people.
• Since some buildings may catch fire due to an earthquake, it is necessary that all buildings, especially tall buildings, have fire fighting equipment in working order.

Question 14: Draw a labelled diagram of a seismograph. Explain its working.

Answer: The tremors produce waves on the surface of the earth. These are called seismic waves. The waves are recorded by an instrument called the seismograph. The instrument is simply a vibrating rod, or a pendulum, which starts vibrating when tremors occur. A pen is attached to the vibrating system. The pen records the seismic waves on a paper which moves under it. By studying these waves, scientists can construct a complete map of the earthquake. They can also estimate its power to cause destruction.

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