NCERT Solutions for Class 8 Science Chapter 15 Some Natural Phenomena

NCERT Solutions for Class 8 Science Chapter 15 Some Natural Phenomena are given below. Here we have provided the best and error-free answers to all the exercise questions that will strengthen your foundation in science. Solving NCERT questions will assist you in grasping the content in the Crop Production and Management chapter in a better way.

In these solutions, we have answered all the intext and exercise questions provided in NCERT class 8 science textbook. NCERT Solutions for Class 8 Science Chapter 15 Some Natural Phenomena provided in this article are strictly based on the CBSE syllabus and curriculum. Students can easily download these solutions in PDF format for free or can read them online.

Some Natural Phenomena Class 8 Science NCERT Solutions

Exercise Questions

Question 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

Answer: (b) A copper rod

Explanation: Only non-conducting materials can be easily charged by friction. Copper is a highly conducting materials. Therefore, a copper rod cannot be charged easily by friction.

Question 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.

Answer: (b) The rod becomes positively charged, while the cloth has a negative charge.

Explanation: When two objects are rubbed against each other, they acquire opposite charges. By the law of convention, it is known that the rod acquires the positive charge and the cloth is acquiring the negative charge.

Question 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 attracts a charged plastic straw. (T / F)

(c) Lightning conductor cannot protect a building from lightning. (T/F)

(d) Earthquakes can be predicted in advance. (T / F)

Answer:
(a) False

Like charges repel each other and unlike charges that attract each other.

(b) True

A charged plastic straw has a negative charge on its surface while the glass rod has positive charges on its surface. Unlike charges attract each other so, they both attract each other.

(c) False

During a lightning, the lightning conductor conducts all the atmospheric charges to the Earth directly, leaving the building safe. Hence, lightning conductors protect a building from lightning.

(d) False

Even though the earthquake causes are known, there are no instruments that are invented to detect them in advance. Therefore earthquakes cannot be predicted in advance.

Question 4: Sometimes, a crackling sound is heard while taking off a sweater during winters. Explain.

Answer: The electric discharge takes place between the body and the sweater due to friction. At the time of electric discharge some energy is released. In this case, energy is released in the form of crackling sound.

Question 5: Explain why a charged body loses its charge if we touch it with our hand.

Answer: Human body is a good conductor of electricity. A charged body loses its charge when we touch it with hand because the charges get transferred through our body to the earth. This phenomenon is known as electric discharge.

Question 6: 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 the Richter scale. This scale has readings from 1 to 10.

The reading of magnitude 3 on the Richter scale would be recorded by a seismograph.

If the Richter scale gives a reading of magnitude 3, then the earthquake is not likely to cause much damage. Generally, an earthquake of magnitudes higher than 5 is considered destructive in nature.

Question 7: Suggest three measures to protect ourselves from lightning.

Answer: Protective measures against lightning are as follows:

(i) Stay in a completely closed place. If you are moving in a car, then remain there until the lightning is over. Close the windows of the car immediately.

(ii) Do not touch any electrical wires, telephone cables, metal pipes, etc.

(iii) Do not bath in running water. This may cause an electric shock.

Question 8: Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?

Answer: Two charged balloons have similar charges on the surfaces. Since like charges repel each other, that’s why one charged balloon is repelled by another charged balloon. When an uncharged balloon is brought near a charged one, the uncharged balloon acquires some opposite charge. Since unlike charges attract each other, therefore a charged balloon attracts an uncharged one.

Question 9: Describe with the help of a diagram an instrument which can be used to detect a charged body.

Answer: An electroscope can be used to detect whether a body is charged or not. The following figure shows a simple electroscope.

It consists of a metal rod. At one end of the rod, two leaves of aluminium foil are fixed and at the other end, there is a metal disc. The leaves of aluminium foil are placed inside a conical flask and the flask is corked to isolate the leaves from air.

When the metal disc is touched with a charged body, the aluminium strips move away from each other. This happens because some of the charges of the body are transferred to the strips through the metal rod. This method of charging a body is called charging by conduction. The nature of charges on both the leaves and the charged body is similar. Hence, both the leaves of the aluminium foil will move away from each other. If the body was not charged, then the leaves of the foil would remain as they were before. They would not repel each other.

Question 10: List three states in India where earthquakes are more likely to strike.

Answer: Three states in India are Gujrat, Rajasthan and Himachal Pradesh.

In India, the areas most threatened are Kashmir, Western and Central Himalayas, the whole of North-East, Rann of Kutch, Rajasthan and the Indo-Gangetic Plane. Some areas of South India also fall in the danger zone.

Question 11: Suppose you are outside your home and an earthquake strikes. What precaution would you take to protect yourself?

Answer: During the earthquake, I would take the following precaution:

• I would try to find a clear spot, away from buildings, trees and overhead power lines. Drop to the ground.
• If I am in a car or a bus, do not come out. Ask the driver to drive slowly to a clear spot. I will not come out till the tremors stop.

Question 12: 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: No. We should not carry an umbrella in a thunderstorm. During thunderstorms, which are accompanied by lightning, electric discharge from the clouds can travel through the metallic rod of the umbrella. This may give an electric shock to the person who is carrying it. Hence, it is not safe to carry an umbrella during lightning.

NCERT Solutions for Class 8 Science Chapter 15 – A Brief Discussion

CBSE Class 8 Science NCERT Solutions Chapter 15 helps students to clear their doubts and to score good marks in the board exam. All the questions are solved by experts with a detailed explanation that will help students complete their assignments & homework. Having a good grasp over CBSE NCERT Solutions for Class 8 Science will further help the students in their preparation for board exams and other competitive exams such as NTSE, Olympiad, etc.