Table of Contents
The NCERT Exemplar Solutions for Class 8 Science Chapter 15 provides a detailed answer to all of the chapter’s questions. When used in conjunction with textbooks, students will be able to increase their exam preparation. It will also eliminate the need for other books to be consulted.
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Chapter 15 – Some Natural Phenomena NCERT Exemplar Solutions for Class 8 Science
Access Answers to the NCERT Exemplar Class 8 Science Chapter 15 – Some Natural Phenomena
Multiple Choice Questions
- An electroscope is a device which is used to find if an object is
(a) charged
(b) magnetic
(c) free of cracks
(d) hot
Answer – (a) charged
Explanation:
A device known as an electroscope is used to determine if an object has an electrical charge. It is composed of two closely positioned metal strips.
- Electric current is to be passed from one body to another. For this purpose, the two bodies must be joined by
(a) cotton thread
(b) plastic string
(c) copper wire
(d) rubber band
Answer – (c) copper wire
Explanation: It is a well-known fact that copper is an excellent conductor of electricity, whereas plastic, rubber, and cotton are poor conductors.
- The movement of the earth’s plates causes
(a) cyclones
(b) lightning
(c) earthquakes
(d) thunderstorms
Answer – (c) earthquakes
Explanation: Earthquakes are caused when the earth’s plates rub against each other, which can result in damage to buildings and structures.
- 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
Answer – (c) they may attract or repel depending on the type of charges they carry
Explanation:
Opposite charges attract each other, while like charges repel each other.
- Which of the following is not likely to cause Tsunami?
(a) A major nuclear explosion undersea
(b) Earthquake
(c) Volcanic eruption
(d) Lightning
Answer – (d) Lightning
Explanation:
Tsunamis are caused by disturbances deep in the ocean, which can be triggered by earthquakes, major undersea nuclear explosions, or volcanic eruptions.
- 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
Answer – (a) the crust of the earth
- 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)
Answer – (a) (i) & (ii)
Explanation:
An earthquake is a sudden shaking or trembling of the earth which lasts for a very short time. Earthquakes are caused due to the movement of plates. Boundaries of the plates are weak zones where earthquakes are most likely to occur.
- The outermost layer of earth is called
(a) mantle
(b) outer core
(c) crust
(d) inner core
Answer – (c) crust
Explanation:
The earth’s top layer is called the crust, which is followed by the mantle, outer core, and inner core.
- Major earthquakes are less likely to occur in
(a) North East India
(b) Rajasthan
(c) Rann of Kutch
(d) Orissa
Answer – (d) Orissa
Explanation:
In India, major earthquakes are less likely to occur in Orissa, while the most vulnerable areas are Kashmir, the Western and Central Himalayas, the entire North-East, the Rann of Kutch, Rajasthan, and the Indo-Gangetic Plain.
- 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)
Answer – (a) (i), (ii) & (iii)
Very Short Answer Questions
- State whether the following are True or False.
(a) Earthquakes occur all the time all over the world.
(b) The plates of the outermost layer of the earth are always in continuous motion.
(c) Tremors on the earth can also be caused by the eruption of a volcano.
(d) The process of electric discharge cannot occur between clouds and the earth.
(e) Bathing outdoors should be avoided during a thunderstorm.
Answer –
- True
- True
- True
- False- The process of electric discharge occurs between clouds and the earth.
- True
- Is it possible to predict the occurrence of an earthquake?
Answer – No, it is not possible to predict the exact occurrence of an earthquake.
- If a charged plastic straw is brought near another uncharged plastic straw, what will happen?
Answer – If a charged plastic straw is brought near another uncharged plastic straw, they will be attracted to each other.
- The aluminium strips in an electroscope as shown in fig. 15.1 are replaced by plastic strips and a charged body is brought in contact with the metal clip. What will happen?
Answer – If plastic strips are used in an electroscope and a charged body is brought in contact with the metal clip, the divergence of the strips will not take place.
- Plastic straws A and B are rubbed with a dry cotton cloth. What will happen if they are brought near each other?
Answer – If plastic straws A and B are rubbed with a dry cotton cloth and brought near each other, they will repel each other.
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Short Answer Questions
- 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.
Answer – No, the lightning conductor will not be effective if it is left hanging in the air by mistake because the charge will not pass through to the earth.
- If air and cloud were good conductors of electricity, do you think lightning could occur? Explain.
Answer – No, lightning will not occur if air and cloud were good conductors of electricity because the separation of charges cannot take place in conductors.
- Identify the lightning conductor and the copper plate in Fig. 15.2.
Answer – In Fig. 15.2, A is the lightning conductor and B is the copper plate.
- 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?
Answer – If the materials used for constructing a building were good conductors, it would not be necessary to install a lightning conductor in the building.
- 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?
Answer – On a dry day, when you touch the screen of a television or computer monitor, you get a slight shock because the electric charge gets accumulated on the screen, and on touching the screen, the charge discharges through our body.
- Explain how does lightning conductor protect a building from getting struck by lightning.
Answer – A lightning conductor protects a building from getting struck by lightning by conducting the charge to the earth, preventing the accumulation of charges on the building.
- 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?
Answer – If a positively charged object is brought in contact with the clip of an electroscope that was earlier provided with a negatively charged body, the negatively charged provided earlier will get neutralised, and the strips will collapse.
- 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.
Answer – If we touch the strips of an electroscope by our hand, the charge in the electroscope strips will get discharged through our hand, and the strips will come back to the original state.
Long Answer Questions
- Explain how lightning takes place?
Answer – Lightning occurs during a thunderstorm due to the separation of charges. The positive charges collect near the upper edges of the clouds, and the negative charges accumulate near the lower edges. When the magnitude of the accumulated charges becomes large, the air cannot resist their flow, and negative and positive charges meet, producing a streak of bright light and sound, called lightning.
- Mention three precautions that you will take to protect yourself if an earthquake strikes when you are inside the house.
Answer – If an earthquake strikes when you are inside the house, take shelter under a table and stay there till the shaking stops, stay away from tall and heavy objects that may fall on you, and if you are in bed, do not get up. Protect your head with a pillow.
- Explain why it is safer to use a wireless telephone instead of a landline telephone during lightning.
Answer –
It is safer to use a wireless telephone instead of a landline telephone during lightning because the electric charge may pass through landline telephone wires, which is dangerous.
- What precautions would you take if lightning occurs while you are outside the house?
Answer – If lightning occurs while you are outside the house, stay away from open vehicles, like motorbikes, tractors, construction machinery, open cars, do not take shelter in open fields, tall trees, shelters in parks and elevated places, do not carry an umbrella when it is lightening, stay away from poles and other metallic objects, squat low on the ground. Place your hands on your knees with your head between the hands.
- 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.
Answer – If the metal clip used in the electroscope is replaced by an ebonite rod and a charged body is brought in contact with it, there will be no effect on the aluminium strips because any charge will not get transferred to the ebonite rod as it is an insulator.
Science Solutions Chapter 15 Some Natural Phenomena FAQs
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