Some Natural Phenomena Class 8 Important Questions and Answers

Important questions of Class 8 Science Chapter 15 Some Natural Phenomena is given below. These important questions will help students while preparing for the exam.  Practising these important questions will analyse their performance and work on their weak points. Score well in exam of Class 8 Science by going through these important questions. Students of Class 8 can download important questions of Class 8 Science Chapter 15 Some Natural Phenomena PDF by clicking the link provided below.

Important Questions of Class 8 Science Chapter 15 Some Natural Phenomena

Here you can get Class 8 Important Questions Science based on NCERT Text book for Class 8. Science Class 8 Important Questions are very helpful to score high marks in board exams. Here we have covered Important Questions on Some Natural Phenomena for Class 8 Science subject.

Very Short Answer Questions

1. What are the three destructive natural phenomena?
Answer:
 Winds, storms and cyclones are the three natural phenomenon which are destructive.

2. Name two other destructive phenomenon.
Answer:
 Lightning, earthquakes.

3. What are the two types of charges?
Answer:
 There are two types of charges:
(i) Positive charges
(ii) Negative charges.

4. What are the interactions of these two types of charges with each other?
Answer:
 (i) Like charges repel each other.
(ii) Unlike charges attract each other.

5. What is lightning?
Answer:
 Lightning is an electric spark on huge scale.

6. What is the cause of lightning?
Answer:
 Lightning is caused by the accumulation of charges in clouds.

7. What is amber?
Answer:
 The amber is a kind of resin.

8. What happens when amber is rubbed with fur?
Answer:
 When amber is rubbed with fur, it attracts light object.

9. What is static electricity?
Answer: 
The electricity generated by rubbing is called static electricity because the charges do not move.

10. Who discovered the static electricity or lightning in clouds?
Answer: 
Benjamin Franklin in 1752.

11. What are charged objects?
Answer:
 The objects which acquire a small charge on rubbing are called charged objects.

12. Write the nature of charges on a glass rod and silk cloth when they are rubbed with each other.
Answer:
 The charge on glass rod is positive while on silk cloth is negative.

13. What is an electric current?
Answer: 
The flow of charges is called electric current.

14. Name the device which is used to test whether an object is charged or not.
Answer:
 Electroscope.

15. Name the material used to transfer of charges from one body to other.
Answer:
 Metallic conductors.

16. What do you mean by earthing?
Answer: 
The process of transferring of charge from a charged body to the earth is called earthing.

17. Write the importance of earthing.
Answer: 
Earthing is provided in building to protect us from electrical shocks due to any leakage of electrical current.

18. What is an electric discharge?
Answer: 
The process of meeting of negative and positive charges to release huge amount of energy is called electric discharge.

19. What are the safe places during thunderstorm?
Answer:
 The covered vehicles and buildings are safe during thunderstorm.

20. When you are in open where should you take shelter?
Answer:
 We should take shelter under small trees.

21. Is sitting on motor cycle safe or not during lightning?
Answer:
 No, it is not safe.

22. What are the harmful effects of lightning on a lightning victim?
Answer: 
Loss of memory, loss of sight or hearing, broken bones etc.

23. Name the device used to save multistorey building from lightning.
Answer:
 Lightning rod conductor.

24. Where is the lightning rod attached to protect the building from lightning?
Answer:
 On the top of the building.

25. Define lightning conductor.
Answer:
 The device which is used to protect the buildings from the effect of lightning.

26. Name some natural phenomenon which can be predicted to some extent.
Answer:
 Thunderstorm, lightning and cyclones.

27. Name a natural phenomenon which cannot be predicted yet now.
Answer:
 Earthquake.

28. What is an earthquake?
Answer:
 An earthquake is a sudden shaking or trembling of the earth which lasts for a very short time.

29. Write the cause of earthquake.
Answer: 
Earthquake is caused by a disturbance deep inside the earth’s crust.

30. What are other natural phenomena caused by earthquake?
Answer: 
Earthquake can cause floods, landslides and tsunamis.

31. What is tsunami?
Answer: 
The earthquake under the oceans is called tsunami.

32. When and where a major tsunami takes place in India?
Answer:
 A major tsunami occurred in the Indian Ocean on 26 December 2004.

33. Is it true that earth is balanced on the horn of a bull, when bull shifts its horn an earthquake takes place?
Answer:
 No. It is not true.

34. Name the instrument used to measure earthquake.
Answer: 
Seismograph.

35. Write the other causes of tremors on earth.
Answer:
 Tremors on earth can also be caused when a volcano erupts, underground nuclear explosion and meteor hits the earth.

36. What are seismic or fault zones?
Answer:
 The weak zones where earthquakes are more likely to occur are called seismic or fault zones.

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

Short Answer Type Questions

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

Answer: Plastic comb gets electrically charged due to rubbing & therefore it attracts tiny pieces of paper which are neutral, as charged body can attracts an uncharged body.

2: Why a copper rod cannot be charged by friction, if held by hand?

Answer: Copper is a conducting object, as soon as it gets charged by rubbing with another material, the electric charge produced on its surface flow through our hand & body into the earth and it remains uncharged.

3: Mention three ways by which a body can be charged.

Answer: Three ways are:

Charging by rubbing: Charging of an object by rubbing it with another object is called charging by rubbing. The body which loses electrons acquires positive charge whereas the body which gains electrons acquires negative charge.

Charging by conduction: Charging a neutral body by bringing it in contact with a charged body is called charging by conduction.

Charging by induction: Charging a neutral body by bringing it near a charged body is called charging by induction

4: What do you mean by earthing? What is the purpose of providing it in buildings?

Answer: The process of transferring of charge from a charged object to the earth is called earthing. For our safety, most of the electrical appliances and the mains of the house are connected to earth, so that we can be prevented from getting an electric shock.

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

Answer: The following precautions should be taken are as follow:

  1. Find a clear spot, away from buildings, trees, poles and electric poles, signboards and overhead power lines and drop to the ground
  2. Do not use elevators if they are available at some place outside your house.
  3. If you are in a car or a bus, do not come out and drive slowly to a clear spot.

6: Suppose you are at home and an earthquake strikes. What precaution would you take to protect yourself?

Answer: The precautions that should be taken are as follow:

  1. Take shelter under a table and stay there only, till the shaking stops
  2. Stay away from the objects which are tall and heavy that may fall on you.
  3. If you are on bed, do not get up and remain there only and protect your head with pillow.

7: Explain earthing.

Answer: The process of transferring of charge from a charged object to the earth is called earthing. For our safety, most of the electrical appliances and the mains of the house are connected to earth, so that we can be prevented from getting an electric shock.

8: What do you mean by lightning conductor?

Answer: Lightning conductor is a device used to protect buildings from the damaging effects of lightning. It runs from the top to the bottom, along the outer wall of the buildings or any other object, which is to be protected. If lightning strikes the buildings or any other objects, then the lightning conductor provides an easy and direct path for the lightning bolt to pass to the ground without effecting them.

9: How an electroscope can be charged through conduction?

Answer: An electroscope is used to detect the charge on a body. A plastic comb is taken and it is rubbed on hair. Now, the plastic comb gets charged. The comb is touched with the electroscope plate. The static charges which are developed on the comb travels down the conducting wire and reach the two leaves of aluminium foil. Similar charges are acquired by both the leaves and as a result, they repel each other. Thus, the method of charging an uncharged body by bringing another charged body directly in contact is called charging by conduction. By this way, an electroscope can be charged through conduction.

10: A crackling sound is heard while taking off sweater during winters. Explain the reason behind this.

Answer: As we know that electrical charges that are generated through friction are static, i.e., they do not move by themselves and Motion of charges constitutes an electric current. When we take off our sweater there is a motion between the charges on the sweater and our body that produces electric current, which produces a crackling sound. Infact we can see a spark if we take off the sweater in the dark.

11: What are tectonic plates?

Answer: The earth’s lithosphere is fragmented into many pieces. Each fragment is called a plate, also called tectonic plate. These plates are in continuous motion i.e. they float over hot magma.

12: Explain seismograph.

Answer: Tremors or vibrations caused by the earthquakes which travel in the form of waves within the earth or along the earth’s surface, are called seismic waves. Seismograph is an instrument which records these seismic waves.

13: Touch the disc of an electroscope with an ebonite rod rubbed with fur. Now bring a glass rod rubbed with silk close to the disc of this electroscope. Explain what do you observe?

Answer: After rubbing, ebonite rod acquires negative charge. Now when it is touched with the metal cap of an electroscope then both the metal cap & the leaves acquire negative charge due to conduction. Because of negative charge on both the leaves, divergence of leaves takes place. After rubbing with silk, glass rod acquire positive charge & when this positive rod is brought near the metal cap of the above negatively charged electroscope then due to induction positive charge gets induced in the leaves as a result collapsing of leaves takes place.

14: What happens when we touch the metal cap of a charged electroscope with our finger? What is the name of this process?

Answer: The leaves of an electroscope collapse as soon as we touch the metal cap with hand because the leaves of the charged electroscope lose charge to the earth through our body in other words leaves are discharged. This process is known as Earthing.

15: What is the nature of charge on the metal cap and on the leaves of the uncharged electroscope when a negatively charged body is brought in contact with its metal cap?

Answer: Nature of charge on the metal cap and on the leaves of the uncharged electroscope is negative.

16: How would you use an electroscope to determine the nature of charge of a charged body?

Answer: Let the electroscope get charged with negative charge, by touching a negatively charged ebonite rod to the metal disc of the electroscope. The leaves of the electroscope open up (diverge). Now touch the body to be tested with the metal disc of the charged electroscope.

  • If the divergence of the leaves increases, the body has similar charge that is the given body is also negatively charged.
  • If the divergence of the leaves decreases, the body has unlike charge that is the given body is positively charged.

17: What are the uses of an electroscope?

Answer: An electroscope can be used for following purposes:
(i) To detect & measure the charge on a body.
(ii) To determine the nature of charge on a body.

18: List two states in India where earthquakes are more likely to strike.

Answer: Two places in India which are most threatened by earthquake are Kashmir and Rann of kutch.

19: Explain why a charged balloon is repelled by another charged balloon but a charged balloon is attracted by a charged balloon?

Answer: The charged balloon has similar charges on its surfaces, since like charges repel each other thus charged balloon repels another charged balloon. When an uncharged balloon is brought near a charged balloon it acquires some opposite charge, since opposite charge attracts each other therefore a charged balloon attracts an uncharged balloon.

20: Why a charged body loses its charge if we touch it with our hand?

Answer: A charged body loses its charge if we touch it with our hand because the charges get transferred from our body to earth, this process is known as earthing.

21: What causes an earthquake?

Answer: The earth’s lithosphere is fragmented into many pieces. Each fragment is called a plate, also called tectonic plate, these plates are in continual motion, when they brush past one another a plate goes under another because of collision, and they cause disturbance in earth’s crust, this disturbance shows up as an earthquake on the surface of earth.

22: What are the causes of sparking?

Answer: Causes of sparking:
(i) On electric pole wires become loose.
(ii) Blowing of wind and shaking the wires.
(iii) Looseness

23: What happens when amber is rubbed of fur?

Answer: When amber is rubbed with fur, it attracts light objects such as hair. In the same way woollen and polyester clothes also attract light objects.

24: Who established the relation between sparks produced by amber and the thunderstorms?

Answer: An American Scientist Benjamin Franklin established that sparks produced by amber are similar to those produced in sky during a thunderstorm. He flew a kite tied with a silken thread, which had an iron key attached to it on a rainy day. During lightning, he felt the shock through iron key, which proved that clouds also carried charges.

25: How can charging take place when the substances are rubbed?

Answer: When a plastic refill is rubbed with polythene, it acquires a small electric charge. Similarly, when a plastic comb is rubbed with dry hair, it also acquires a small charge. These objects are called charged objects. In this process of charging the refill and the plastic comb, polythene and hair also get charged.

26: How many different types of charges are there? Write the nature of charges on glass rod and silk cloth when they are rubbed each other? 

Answer: There are two types of charges:
 (i) Positive charge and
 (ii) Negative charge
Charge acquired by a glass rod rubbed with silk is called positive charge and the charge acquired by silk cloth is called negative charge.

27: What is static electricity? How is it different from electric current?

Answer: The electrical charges generated by rubbing produce static electricity. The charges do not move in static electricity while charges move in current electricity.

28: What is electric discharge? How does it occur?

Answer: The negative and positive charges meet, producing streaks of bright light and sound. This process is called electrical discharge, the process of electric discharge can occur between two or more clouds or between clouds and earth.

29: How does electric discharge occur in clouds?

Answer: At the time of thunder negative charges get accumulated near the clouds and positive charges accumulate near ground. When these charges meet electric discharge takes place between ground and clouds. In this process a large amount of energy is released as thunder and lightning.

30: During lightning what should we do?

Answer: (i)Hearing thunder is an alert to rush to a safer place.
(ii) After hearing the last thunder wait for some time before coming out.

31: What is lightning conductor? How does it protect building from lightning?

Answer: Lightning conductor is a device used to protect building 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 transfer of electric charge to the ground.

Class 8 Science Chapter 15 Some Natural Phenomena Important Question 1

32: What is an earthquake? How does it occur?

Answer: An earthquake is a sudden shaking or trembling of earth which lasts for a very short time. It is caused by a disturbance inside the earth’s crust. There can be a great loss to life and property. They can cause flood, tsunami and landslides. The magnitude of the earthquake is measured by an instrument called seismograph and it is measured on Richter Scale.

33: Write about two last major earthquakes in India.

Answer: (i) A major earthquake occurred on 26 January 2001 in Bhuj district of Gujarat.
(ii) A major earthquake also occurred in India on 8 October 2005 in Uri and Tangdhar towns of North Kashmir.

34: Name the regions of the earth more prone to earthquakes.

Answer: Earthquakes are caused by the movement of plates. The regions which fall on the boundaries of these plates are called danger zones. Earthquakes are most likely to happen in these danger zones.

35: What are fault zones? Name the fault zones in India.

Answer: The areas fall between the boundaries of two plates are called weak zones or seismic or fault zones. In india the most threatened areas are Kashmir, Western and Central Himalayas, whole of North-East, Rann of Kutch, Rajasthan, Indo-Gangetic plain and some areas of south India.

Class 8 Science Chapter 15 Some Natural Phenomena Important Question 2

36: What are the protections to be taken against earthquakes?

Answer: If you are at home:
1. Take shelter under the table and stay there until the stoppage of shaking
2. Keep yourself away from the tall or heavy objects that may fall on you and damage you.
3. If you are on bed, do not get up and keep a pillow on your head

If you are outside the home:

1. Find a clear spot, away from buildings, trees, poles and electric poles, signboards and overhead power lines and drop to the ground.
2. Do not use elevators if they are available at some place outside your house
3. If you are in a car or a bus, do not come out and drive slowly to a clear spot.

37: What are the protections to be taken against lightning?

Answer: During lightning avoid going at an open place, try to rush towards safe place like in a house or building, if you are travelling in nay vehicle like car or bus, you are safe inside with windows and doors of the vehicle closed. If you are in a forest take shelter under a smaller tree.

38: Explain a lightning conductor and its function.

Answer: Lightning conductor is the device that protects a tall building from lightning strike, by providing an easier path for current to flow to earth than through the building. It consists of a thick copper strip of very low resistance connected to the ground below. A good connection to the ground is essential and is made by burying a large metal plate deep in the damp earth. In the event of a direct lightning strike, the current in the conductor may be great as to melt or even vaporize the metal, but the damage to the building will nevertheless be limited.

39: List the things that you should do while thunderstorm.

Answer: During lightning avoid going at an open place, try to rush towards safe place like in a house or building, if you are travelling in nay vehicle like car or bus, you are safe inside with windows and doors of the vehicle closed. If you are in a forest take shelter under a smaller tree.

40: List the things that you should not do while thunderstorm.

Answer: During lightning avoid going at an open place, try to rush towards safe place like in a house or building, if you are travelling in nay vehicle like car or bus, you are safe inside with windows and doors of the vehicle closed. If you are in a forest take shelter under a smaller tree.

Long Answer Type Questions

1: Define the following
(a) Lightning
(b) Earthing

Answer: 
(a) Lightning: Lightning is a natural phenomenon that has fascinated people for ages. Several people thought and researched about the cause of lightning and its process. Benjamin Franklin discovered for the first time that there is an electric discharge between clouds that produces a spark, and it is the electric spark between the clouds and the earth that appears as lightning. His famous kite experiment proved this fact. The occurrence of lightning is as follows. The formation of clouds involves friction between water particles in the atmosphere. The friction charges the particles. Among the positive and negative charges, the negative charge accumulates at the bottom of the cloud and the positive charges in its top. As the accumulation of the charge increases, the cloud will create a positive charge on the ground nearby. As the amount of charge increases, the negative charge on the cloud tends to make a path towards the ground, and it results in a narrow streak of electrical discharge, which we call lightning.

(b) Earthing: The process of transferring of charge from a charged object to the earth is called as earthing. For our safety, most of the electrical appliances and the mains of the house are connected to earth, so that we can be prevented from getting an electric shock.

2: Define the following:
(a) Richter scale
(b) Seismograph

Answer: (a) Richter scale: The Richter scale is used to rate the magnitude of an earthquake that is the amount of energy it released. This is calculated using information gathered by a seismograph.

(b) Seismograph: Tremors or vibrations caused by the earthquakes which travel in the form of waves within the earth or along the earth’s surface, are called seismic waves. Seismograph is an instrument which records these waves.

3: Explain an electroscope and earthing.

Answer: An electroscope is a device that detects the type of charge on a body. Like charges repel and unlike charges attract each other. This is used in an electroscope. An electroscope consists of a glass jar fitted with a cork lid and a metallic wire passing through it. There are two metallic strips at the bottom of the wire. The upper end of the wire is connected to a metal disc. A body that is positively charged is touched to the metal disc, so that the charge is transferred to the metal strips through the wire, and they diverge from each other on gaining a like charge. Now, if a negatively charged object is brought into contact with the disc, the strips converge towards each other, indicating the unlike charge on the body. Similarly, if a positively charged body is brought in contact with the metal disc, the divergence of the metal strips increases, indicating the like charge on the body.

Class 8 Science Chapter 15 Some Natural Phenomena Important Question 3

The process of transferring of charge from a charged object to the earth is called earthing. For our safety, most of the electrical appliances and the mains of the house are connected to earth, so that we can be prevented from getting an electric shock.

4: Explain two natural destructive phenomena.

Answer: Lightning:
During the development of a thunderstorm, the air currents move upward while the water droplets move downward. These vigorous movements cause separation of charges. By a process, not yet completely understood, the positive charges collect near the upper edges of the clouds and the negative charges accumulate near the lower edges. There is an 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. Accumulation of charge leads to lightning.
The process of electric discharge can occur between two or more clouds, or between clouds and the earth. A lightning strike could destroy life and property. It is therefore, necessary to take measures to protect ourselves.

Earthquake:
An earthquake is a sudden shaking or trembling of the earth lasting for a very short time. It is caused by a disturbance deep inside the earth’s crust.
Earthquakes occur all the time, all over the earth. They are not even noticed. Major earthquakes are much less frequent. They can cause immense damage to buildings, bridges, dams and people. There can be a great loss to life and property.

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. However, most earthquakes are caused by the movement of earth’s plates.

Since earthquakes are caused by the movement of plates, the boundaries of the plates are the weak zones where earthquakes are more likely to occur. The weak zones are also known as seismic or fault zones. 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. However, most earthquakes are caused by the movement of earth’s plates. The power of an earthquake is expressed in terms of a magnitude on a scale called Richter scale. Really destructive earthquakes have magnitudes higher than 7 on the Richter scale.

5. Explain the construction and working of electroscope.

Answer: It is an instrument used to detect electric charges. A simple electroscope can be constructed as follows.
(i) Take a glass container.
(ii) Insert a metal wire inside it.
(iii) To the ends of the wire, which are inside the jar, attach 2 metal plates(say aluminium plates).
(iv) The other end is outside the glass container is connected or brought in contact with charged body.

Class 8 Science Chapter 15 Some Natural Phenomena Important Question 4

Working of An Electroscope:
(i) In an uncharged electroscope, the leaves hang straight down.
(ii) When a charged object touches the metal knob, electric charges travel down the rod and into the leaves.
(iii) The leaves spread apart, indicating the presence of an electric charge.
(iv) Since the charge on both leaves is the same the leaves repel each other and spread out.

6. Explain the mechanism of thunderstorms.

Answer: During the development of a thunderstorm, the air currents move upward while the water drops move downward. These movements cause separation of charges. The positive charges collect near the upper edges of the clouds and negative charges accumulate near the lower edges. There is accumulation of positive charges near the ground also. When the amount of 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. This process is called an electric discharge. The process of electric discharge can occur between two or more clouds or between clouds and the earth. In this way thunderstorm is caused.

7. How can you save yourself from lightning?

Answer: Some safety measures are:
(i) We should run to take shelter in the house.
(ii) We should remain in the covered area.
(iii) We should not sit in open, on scooters or bike etc.
(iv) We should take shelter under a small tree while in open.
(v) If there is no tree or other shelter we should sit with head folded.
(vi) We should plug out all the electrical appliances during lightning.
(vii) We should not use wired telephones during lightning. Mobiles and cordless phones are safe.

8. Explain the safety measures during thunderstorm when you are inside your home.

Answer: Some safety measures are as follows:
(i) During a thunderstorm contact with telephone cords, electrical wires and metal pipes should be avoided.
(ii) It is safer to use cordless phones and mobiles.
(iii) Bathing should be avoided during thunderstorm.
(iv) Computer, TV etc. should be unplugged.

9. Explain the mechanism of earthquakes.

Answer: The tremors are caused by the disturbance deep down in the uppermost layers of earth. The uppermost layer of earth is called crust. The crust of earth is not a 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 disturbances and show up as an earthquake on the surface of the earth. Although we know the causes of the earthquake, it is not possible to predict when and where the next earthquake might occur.

Class 8 Science Chapter 15 Some Natural Phenomena Important Question 5

10. What is a seismograph? How does it work?

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

11. What suggestions will you give the people to make ‘Quake Safe’?

 Answer: Some suggestions are:
(i) Consult qualified architects and structure engineers.
(ii) Make the structure symmetrical so that the mass is distributed uniformly.
(iii) Use of mud or timber is better than the heavy construction.
(iv) The cupboards and shelves are to the walls.
(v) Be careful about where to hang wall clocks, photo frames, water heater etc. So that in the event of an earthquake they do not fall on people.
(vi) All building should have fire fighting equipment installed.

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