NCERT Exemplar Class 8 Science Solutions Chapter 15 Some Natural Phenomena

Multiple Choice Questions

1. An electroscope is a device that is used to find if an object is 

(a) Charged 

(b) Magnetic 

(c) Free of cracks 

(d) Hot 

Ans: The correct answer is Option (a). 

The electroscope is a means that determines if the device is charged or uncharged. It is composed of two metallic strips that are positioned in close proximity to each other. 

2. Electric current is to be passed from one body to another. For this purpose, the two bodies must be joined by 

(a) Cotton threads 

(b) Plastic string 

(c) Copper wire 

(d) Rubber band 

Ans: The correct answer is Option (c).

From the above-given Option, only copper permits the conduction of electricity. Thus, copper is the appropriate choice. 

3. The movement of the Earth's plates causes 

(a) Cyclones     

(b) Lightning 

(c) Earthquakes 

(d) Thunderstorms 

Ans: The correct answer is Option (a). 

The earthquake is caused by the sudden movement of the tectonic plates underneath the Earth's surface.

4. Two charged objects are brought close to each other. Choose the most appropriate statement from the following options: 

(a) They may attract 

(b) They may repel 

(c) They may attract or repel depending on the type of charges they carry 

(d) There will be no effect 

Ans: The correct Option is (c).

The attraction and repulsion depend on the charge on the object. If both the objects are positively or negatively charged, they will repel each other. And if the objects are oppositely charged, they will attract each other. 

5. Which of the following is not likely to cause a Tsunami? 

(a) A major nuclear explosion under the sea 

(b) Earthquake 

(c) Volcanic eruption 

(d) Lightning 

Ans: The correct Option is (d).

A tsunami is caused by an earthquake, or explosion under the sea or a volcanic eruption. There is no relation between a Tsunami and lightning as the latter has no energy to start it.

6. The Earth's plate responsible for causing earthquakes is 

(a) The crust of the Earth 

(b) The mantle of the Earth 

(c) The inner core of the Earth 

(d) The outer core of the Earth 

Ans: The correct Option is (a).

An abrupt movement in the top layer of the Earth, i.e. the crust, results in an Earthquake.

7. Consider the list of terms given below: 

(i) Seismic Zone 

(ii) Fault Zone 

(iii) Mantle 

(iv) Inner Core 

The boundaries of the Earth's plate are known as 

(a) (i) & (ii) 

(b) (i) & (iii) 

(c) (iii) & (iv) 

(d) (ii), (iii) & (iv) 

Ans: The correct Option is (a) (i) & (ii) 

8. The outermost layer of Earth is called 

(a) Mantle 

(b) Outer core 

(c) Crust 

(d) Inner core 

Ans: The correct Option is (c) Crust 

9. Major earthquakes are less likely to occur in 

(a) North East India 

(b) Rajasthan 

(c) Rann of Kutch 

(d) Orissa 

Ans: The correct Option is (d) Orissa 

10. Consider the list of terms given below 

(i) Tsunami

(ii) Landslide 

(iii) Floods 

(iv) Lightning 

Earthquakes can cause 

(a) (i), (ii) & (iii) 

(b) (ii) & (iv) 

(c) (ii), (iii) & (iv) 

(d) (iii) & (iv) 

Ans: The correct Option is (a) (i), (ii) & (iii)

Very Short Answer Questions

11. State whether the following are True or False. 

(a) Earthquakes occur all the time all over the world. 

Ans: True 

(b) The plates of the outermost layer of the Earth are always in continuous motion. 

Ans: True 

(c) Tremors on the Earth can also be caused by the eruption of a volcano. 

Ans: True 

(d) The process of electric discharge cannot occur between clouds and the Earth. 

Ans: False- The electric discharge (flow of electrons) can occur between the clouds and the Earth.

(e) Bathing outdoors should be avoided during thunderstorms. 

Ans: True 

12. Is it possible to predict the occurrence of an earthquake? 

Ans: No, the prediction of an earthquake is not possible. 

13. If a charged plastic straw is brought near another uncharged plastic straw, what will happen? 

Ans: The charged and uncharged plastic straw will have opposite charges. So, they will get attracted because of the electrostatic force.

14. The aluminium strips in an electroscope, as shown in fig. are replaced by plastic strips, and a charged body is brought in contact with the metal clip. What will happen? 

Ans: The plastic strips are insulators, so they cannot conduct any charge. Thus, there will be no divergence among the strips when they come in contact with the charged body.

15. Plastic straws A and B are rubbed with a dry cotton cloth. What will happen if they are brought near each other? 

Ans: Rubbing the plastic strips will create a charge on them, and they will get repelled.

Short Answer Questions

16. During the construction of a building, the lightning conductor was left hanging in the air by mistake. Would the lightning conductor be still effective? Explain. 

Ans: For the lightning conductor to work correctly, it must be connected with the Earth. If it is left hanging in the air, it won't conduct any charge and thus will not be effective.

17. If air and clouds were good conductors of electricity, do you think lightning could occur? Explain. 

Ans: Splitting of charges will not occur in conductors, and so lighting will not occur. This is because charges do not collect on clouds.

18. Identify the lightning conductor and the copper plate in Fig. 15.2. 

Ans: In the figure above, the part marked as A is the lighting conductor and B is the copper plate.

19. If the materials used for constructing a building were good conductors, do you think lightning will strike the building? Will the lightning conductor be still required to be installed in the building? 

Ans: Installation of a conductor is not required if the materials used to create the building are good conductors.

20. You might have observed on a dry day that when you touch the screen of a television or computer monitor (with a picture tube), you get a slight shock. Why does it happen? 

Ans: There is humidity on the TV screen, on which the electric charge builds up. This allows the charges to escape, and when we contact the screen, we get a slight shock.

21. Explain how lightning conductors protect a building from getting struck by lightning. 

Ans: When lightning strikes a building, electrons transfer to the Earth. The lightning conductor helps to transmit the charges in the Earth and saves the building.

22. In an electroscope, if a negatively charged body is brought in contact with the metal clip, the strips of the electroscope diverge. If now another charged object carrying an equal amount of positive charge is brought in contact with the clip, what will happen? 

Ans: When the electroscopic clip comes into touch with a negatively charged substance, it becomes positively charged and becomes neutral. This will lead to their collapse.

23. The strips of an electroscope diverge when a charged body is brought in contact with the metal clip. Now the clip is touched gently by our hand. What will happen to the strips? Explain.

Ans: When the electroscope is touched with bare hands, the charge on it gets discharged. This is why the strips retain their original position.

Long Answer Questions

24. Explain how lightning takes place? 

Ans: During the thunderstorm, water droplets fall to the ground, and air currents rise. This phenomenon causes the parting of charges. The bottom edge of the clouds collects negatively charged ions, whereas the top edge collects positively charged ions. Positively charged ions are also present on the surface of the Earth. When this collection reaches a certain level, the airflow slows down. This causes a collision of negatively and positively charged ions, resulting in lightning and sound.

25. Mention three precautions that you will take to protect yourself if an earthquake strikes when you are inside the house. 

Ans: You can take the following precautions during an earthquake-

(i) Hide under a sturdy table. 

(ii) Avoid things that are too heavy or too tall. 

(iii) Do not get out of bed if you are asleep. Use a pillow to cover your head.

26. Explain why it is safer to use a wireless telephone instead of a landline telephone during lightning. 

Ans: A telephone cable's wire is linked to a pole. Lightning can release electricity on a pole, which can then reach the telephone you're operating. Because a human will handle the receiver, it may cause shocks as there will be electricity in the receiver's wire. On the other hand, a wireless phone is not connected to any wire. Nothing will happen in it. As a result, using a wireless phone during lightning strikes is far secure than using a landline.

27. What precautions would you take if lightning occurs while you are outside the house? 

Ans: You can take the following precautions outside the house during lightning- 

(i) Do not stand beneath a tree because lightning can strike. 

(ii) Avoid touching metal things like poles. 

(iii) Prefer not to roam with an umbrella in an open place. 

(iv) Keep a safe distance from cars with open doors. It doesn't matter what size it is.

28. If the metal clip used in the electroscope is replaced by an ebonite rod and a charged body is brought in contact with it, will there be any effect on the aluminium strips? Explain.

Ans: An ebonite rod cannot conduct charge as it is an insulator, so there will be no charge transfer. Thus, the aluminium strips will not deflect due to repulsion.

Introduction Chapter 15 -Some Natural Phenomena

Class 8 Science NCERT Exemplar Solutions Chapter 15 Some Natural Phenomena provides students solutions to all the questions which are given in the NCERT exemplar class8 science book. Studying these exemplar questions will help you to get ready for your final examination. The Exemplar solutions prepared by Vedantu provides you with answers to all types of questions and ensure 100% accuracy. Candidates who want to top in Class 8 exams should go through NCERT exemplar solutions. It is prepared in simple language so that you can learn and understand it easily.

Chapter 15- natural phenomena include study about different types of natural phenomena, why they occur, and how you should be safe during that time. This chapter covers two main natural phenomena:

• Earthquake

• Lightning

Also, in this chapter students will learn about the different ways to produce electric charges. You can study NCERT exemplar solutions to know the pattern of questions that can be framed in this chapter. You can get a better understanding of this chapter if you complete your NCERT exemplar solution and then you will surely score more marks.

Important Topics - Chapter 15 - Natural Phenomena