# MP Board Class 8th Science Solutions Chapter 15 Some Natural Phenomena

## MP Board Class 8th Science Solutions Chapter 15 Some Natural Phenomena

### MP Board Class 8th Science Some Natural Phenomena NCERT Textbook Exercises

Select the correct option in questions 1. and 2.

Question 1.
Which of the following cannot be changed easily by friction?
(a) A plastic scale
(b) A copper rod
(c) An inflated balloon
(d) A woolen cloth.
(b) A copper rod

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.
(b) Becomes positively charged while the cloth has a negative charge.

Question 3.
Write ‘T against true and ‘F’ against False in the following statements:

1. Like charges attract each other.
2. A charged glass rod attract a charged plastic straw.
3. Lightning conductor cannot protect a building from lightning.
4. Earthquakes can be predicted in advance.

1. False
2. True
3. False
4. False.

Question 4.
Sometimes, a crackling sound is heard while taking off sweater during winters. Explain.
This occurs due to electric discharge between sweater and body. Some energy is always released with electric discharge, which in this case is released in the form of a crackling sound.

Question 5.
Explain why a charged body loses its charge if we touch it with our hand.
When we touch a charged body, it loses its charge due to the process of earthing. Our body is a good conductor of electricity and transfers the charges to the earth.

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?
The destructive energy of an earthquake is measured on Richter Scale. The magnitude 3 on this scale can be recorded by a seismograph. Such an earthquake rarely causes damage.

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

1. Find a safe place like a house or a building. If travelling by a bus or by a car, stay inside with windows and doors of the vehicle shut.
2. If outside, take shelter under shorter trees. Stay away from tall trees and poles. Do not lie on the ground but sit placing your hands on your knees, with your head between the hands.
3. If inside, avoid bathing, unplugging electric appliances like TV, computer and switching off air conditioners.

Question 8.
Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?
A charged balloon is repelled by another charged balloon because both have the same charge. And we know similar charges repel each other. But a charged balloon attracts an uncharged balloon and lose its own charge to the other balloon.

Question 9.
Describe with the help of a diagram an instrument which can be used to detect a charged body.
Electroscope is a device used to detect the presence of charge on an object or body. When the metal strips repel each other, that proves that the body is charged. As repulsion is the sure test to detect if a body carries charge or not.

Question 10.
List three states in India where earthquakes are more likely to strike.
Kashmir, Gujarat and Rajasthan.

Question 11.
Suppose you are outside your home and an earthquke strikes. What precautions would you take to protect yourself?
If we are outside and an earthquake strikes, we should take the following precautions:

1. We should find a clear spot away from buildings, trees and overhead power lines.
2. If we are in a bus or a car, do not come out. Ask the driver to drive slowly to a clear spot.
3. Do not come out of bus or car 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.
During thunderstorm, we should not carry an umbrella. An umbrella can become electrically charged due to lightning. It can be dangerous to life during thunderstorm. Therefore, carrying an umbrella is not proper during thunderstorm.

### MP Board Class 8th Science Some Natural Phenomena NCERT Extended Learning – Activities and Projects

Question 1.
Open a water tap. Adjust the flow so that if forms a thin stream. Charge a refill. Bring it near the water stream. Observe what happens. Write a short report on the activity.
Do yourself.

Question 2.
Make your own charge detector. Take a paper strip roughly 10 cm x 3 cm. Give it a shape as shown in Fig 15.2. Balance it on a needle. Bring a charged body near it. Observe what happens. Write a brief report, explaining its working.

Do yourself.

Question 3.
This activity should be performed at night. Go to a room where there is a fluorescent tube light. Charge a balloon. Switch off the tube light so that the room is completely dark. Bring the charged balloon near the tube light. You should see a faint glow. Move the balloon along the length of the tube and observe how glow changes.
Caution: Do not touch the metal parts of the tube or the wires connecting the tube with the mains.
Do yourself.

Question 4.
Find out if there is an organisation in your area which provides relief to those suffering from natural disaster. Enquire about the type of help they render to the victims of earthquakes. Prepare a brief report on the problems of the earthquake victims.
Several NGOs extend help in time of natural disaster. These organisations provide relief to the victims with food packets, blankets, water bottles etc. They help government in their rehabilitation.

### MP Board Class 8th Science Some Natural Phenomena NCERT Additional Important Questions

Question 1.
Name any three natural phenomena.
Earthquakes, cyclones and lightning.

Question 2.
What is static electricity?
The electrical charge generated by rubbing is called static electricity because these charges do not move.

Question 3.
What happens when a charged eraser is brought close to charged balloon?
They would attract each other because there is attraction between opposite charges.

Question 4.
What is earthing?
The process of transfer of charges from a charged object to the earth is called earthing.

Question 5.
What is an earthquake?
An earthquake is the sudden shaking of the earth which lasts for a very short time.

Question 6.
What happens when earthquake occurs?
The earthquake causes immense damage to buildings, bridges, dams and people. There can be great loss of life and property. The earthquake can cause floods, landslides and tsunamis. Thousands of people may lose their lives.

Question 7.
What did Ancient Greeks know about amber?
Ancient Greeks knew as early as 600 BC that a resin names amber, when rubbed with fur, acquired some properties, which attracted objects with lightweight towards it. They knew that if amber is rubbed for longer period, it produced sparks as seen in sky during thunderstorm.

Question 8.
How does electrical discharge take place in clouds?
During thunderstorms the negative charges get accumulated near the clouds and positive charges accumulate near the ground. When these negative and positive charges meet, electrical discharge takes place between clouds and grounds. It produces a huge amount of energy which is released in the form of lightning and thunder.

Question 9.
What precautions should we take to secure ourselves from lightning stroke during thunderstorm when we are in our homes?
Following precautions should be taken while in house:

• We should not use wired phone.
• Electrical appliances should be plugged off.
• We should not bathe in running water.

Question 10.
How would you protect yourself when an earthquake strikes?