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Online Education for Class 8 Science Chapter 15 Extra Questions and Answers Some Natural Phenomena
Some Natural Phenomena Class 8 Questions And Answers Pdf Question 1.
What happens when a charged balloon is brought close to another charged balloon?
They repel each other.
Some Natural Phenomena Question Answer Question 2.
Why does a charged eraser when brought close to another charged rubber, repel each other?
Because similar charges repel each other.
Class 8 Science Chapter 15 Short Question Answer Question 3.
What happens when a charged eraser is brought close to charged balloon and why?
They would attract each other because opposite charges attract.
Some Natural Phenomena Class 8 Questions And Answers Question 4.
Why does a charged glass rod attract a charged plastic straw? Give reason.
There are two opposite charges, therefore, they attract each other.
Some Natural Phenomena Class 8 Question Answer Question 5.
Are metals good conductors?
Yes, all metals are good conductors.
Ch 15 Science Class 8 Question Answer Question 6.
Why do paper strips receive the same charge from the charged refill through the metallic needle?
Because metals are good conductors of electricity. So, it contributes same charge to the paper strips through the metallic needle.
Class 8 Science Chapter 15 Some Natural Phenomena Question Answer Question 7.
What happens when person touches the metallic wire of an electro¬scope after charging of foil strips? Give reasons for your answer.
When a person touches the metallic wire of an electroscope after charging its foil strips; the foil strips collapse. It happens so because the foil strips lose charge to the earth through human body which is a good conductor of electricity.
Chapter 15 Science Class 8 Question 8.
Is carrying umbrella during thunderstorms advisable? Why?
No, carrying umbrella during the thunderstorm is not advisable, because lightning may strike on the person carrying the umbrella due to its pointed rod.
Some Natural Phenomena Class 8 Solutions Question 9.
If one is in the forest, where should he take shelter during’ thunderstorm?
The person should take shelter under the shortest trees around him.
Extra Questions For Class 8 Science With Answers Question 10.
During thunderstorms, which phone, should be used mobile phone, cordless phone or landline?
It is safe to use mobile phones and cordless phones.
Ncert Science Book Class 8 Extra Questions With Answers Question 11.
Should one take bath during thunderstorm?
Bathing should be avoided during thunderstorm to avoid contact with running water.
Extra Questions For Class 8 Science Question 12.
What would you do with T.V., computers, etc. during thunderstorms?
These should not be played, instead, these should be unplugged.
Extra Questions Of Science Class 8 Question 13.
What parts of human body are damaged by lightning?
Damage to nervous system, burn injuries, loss of hearing or sight, short-term memory loss, broken bones, etc., can occur due to lightning.
Extra Questions Class 8 Science Question 14.
Can you predict the occurrence of earthquakes?
No, prediction of earthquake is not possible.
Ncert Solutions For Class 8 Science Extra Questions Question 15.
When did the last major earthquake take place in India and where?
The last major earthquake in India occurred on 8th of October 2005 in Uri and Tangdhar towns of north Kashmir.
Is Richter a linear scale?
No, Richter scale is not a linear scale.
What is responsible for sparks in the sky?
Electricity is responsible for this phenomenon.
Which phenomenon is yet to be predicted?
It is an earthquake.
What was known to ancient Greeks about amber?
The ancient Greeks knew as early as 600 BC that amber (a kind of resin), when rubbed with fur, attracted light objects such as hairs, twigs, etc.
If amber is rubbed for long enough, what happens as per Greeks?
As per Greeks when amber is rubbed for long enough, it could even generate a spark.
What happens when a plastic scale is rubbed on dry hair? Why?
If plastic scale is rubbed on dry hair, the scale can attract very small pieces of paper because the scale develops charge on rubbing.
What happens when a plastic refill is rubbed with polythene?
When a plastic refill is rubbed with polythene, it acquires a small electric charge (negative).
How many types of charges are there? What happens between two like charges and between two unlike charges if brought closer?
There are two types of charges – positive charges and negative charges. When two like charges are brought closer, they repel each other. When two, unlike charges, are brought closer to one another, they attract each other.
What type of charges are there on plastic straw and glass rod?
There is a negative charge on the plastic straw and is positive charge on glass rod. That is why they attract one another.
What name is given to the electrical charge generated by rubbing?
The electrical charge generated by rubbing is called static electricity because these charges do not move.
What name is given to the electricity generated when charges move?
When the charges move from one conducting body to another, they generate electricity called current electricity.
What is meant by the term earthing? What is its advantage?
The process of transfer of charges from a charged object to the earth is known as earthing. It is provided iri the electrical wiring in buildings to protect people from electrical shock due to any leakage of the electric current.
What happens during the development of a thunderstorm?
During the development of a thunderstorm, the air currents move upward while the v water droplets move downward. This vigorous movements cause separation of charges.
Which is the safest place during the lightning and thunderstorms?
A house or building is the safest place. If someone is travelling by a car or by bus, he/she is safe inside with windows and doors of the vehicle shut.
What are the destruction caused by the natural phenomena like thunderstorms, cyclones and lightning?
Can these phenomena be predicted?
These natural phenomena can cause large scale destruction of human life and property. Yes, these phenomena, fortunately: can be predicted to some extent. The weather department can warn about a thunderstorm developing in some areas.
What is an earthquake? How does it take place?
An earthquake is a sudden shaking or trembling of the earth. It is caused by a disturbance deep inside the earth’s crust.
What are seismic waves? Name the instrument that records these waves.
The waves produced on the surface: of the earth by tremors are called the seismic waves. These waves are recorded by an instrument called the Seismograph.
How is the power of an earthquake expressed? What is the magnitude of destructive earthquakes on this scale?
The power of an earthquake is expressed in terms of magnitude on a scale called Richter scale. On this scale, the destructive earthquakes have magnitudes higher than.
Which areas in India are prone to earthquake?
In India, Kashmir, western and Central Himalayas, the whole of North-East, Rann of Kachchh, Rajasthan and Indo-Gangetic, Plain are prone to earthquake. Some areas of south India also fall in the danger zone.
If an earthquake is of magnitude 2 in this scale. Would it cause much damage?
No, it will not cause much damage. Destructive energy of an earthquake is measured on the Richter scale. The earthquake measuring 7 or more on Richter scale can cause severe damage to life and property.
What are the safety measures against lightning?
During thunderstorms and lightning, no place outside is safe. That is why hearing a thunder we should rush to a safer place.
A house or a building is the safest place. If anybody is travelling by a car or bus, he/ she is safe inside with windows and doors of the vehicle shut.
Describe the meaning, use and construction of lightning conductor.
Lightning conductor is a device used to protect tall buildings from the effect of lightning. Construction: A metallic rod taller than the height of 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 fixed in the ground.
Use: Lightning rod provides easy route for transfer of electric discharge to the ground.
Precaution: It should not be touched during a thunderstorm.
If a thunderstorm occurs, what should you do?
If a thunderstorm occurs, there is always a possibility of lightning and cyclone accompanying it. So, it is better for us to take measures to protect ourselves from the damage caused by these events. Inside the house, one should avoid using telephone, television, etc.
Bathing should be avoided during the thunderstorm to avoid contact with running water. Electrical appliances should be plugged off. If someone is outside, he/she should take shelter under shorter tree. When someone is in the open field, he/she should stay away from tall tree, electric poles, etc.
What are the damages caused by the earthquake? Name the place where some major earthquakes occurred recently.
Earthquake is a natural phenomenon, which we are not yet able to predict. It can cause damage to human life and property on a large scale. The earthquake can cause floods, landslides and tsunami.
The last major earthquake which occurred in India was on 8th October 2005 in Uri and Tangdhar towns of North Kashmir. Before that, a major earthquake occurred on 26th January 2001 in Bhuj district of Gujarat.
What is weak zone or fault zone? Name some of these zones in India.
Since earthquakes are caused by the movements of plates, the boundaries of the plates are the weak zones of fault zone, where earthquakes are more likely to occur. In India, the areas most threatened are Kashmir, Western and Central Himalayas, the whole of North-East, Rann of Kachchh, Rajasthan and the Indo-Gangetic Plain. Some areas of South India also fall in the danger zone.
What is a Richter scale? Is it linear? What are the magnitudes of earthquakes that can cause severe damage to life and properties?
The power of an earthquake is expressed in terms of magnitudes on a scale called Richter scale. This scale is not linear. The earthquake of magnitude 7 or more is destructive and can cause severe damage to life and property.
What are the suggestions that can be followed to protect buildings against earthquakes?
Given below are the suggestions that can be followed to protect buildings against earthquakes :
- The buildings should be so designed that they become ‘Quake Safe’. For this purpose, qualified architects and structural engineers should be consulted.
- In highly seismic areas, the use of mud or timber is better than using heavy construction material. Roofs should be kept as light as possible. In case the structure falls, the damage will not be heavy.
- Cupboards and shelves should be fixed to the walls so that they do not fall easily.
- Since some buildings may catch fire due to an earthquake, it is necessary that all buildings, especially tall buildings, have fire fighting equipment in working order.
What steps should be taken for protection if an earthquake strikes?
In the event that an earthquake does strike, the following steps should be taken for protection :
(A) At home:
- One should take shelter under a table and stay there till shaking stops.
- One should stay away from windows.
- One should stay away from tall and heavy objects that may fall on him/her.
- If anybody is in bed, he/she should not get up but protect his/her head with a pillow.
(B) Outdoors :
- One should find out a clear spot away from buildings, trees and overhead powerlines and drop to the ground.
- If anybody is in a car or a bus, he/she should not come out. Instead, the driver should be asked to drive slowly to a clear spot and should not come out till the tremors stop.
What are the causes of earthquakes? Describe the major cause.
Causes of earthquakes :
- Movement of the earth’s plates (major cause): The outermost layer of the earth is not in one piece. It is fragmented. Each fragment is called a plate. These plates are in continuous motion. The boundaries of the plates are the weak zones, where earthquakes are more likely to occur due to sliding of one plate over or below the other. The weak zones are also known as seismic or fault zones.
- Volcanic eruption.
- Underground nuclear explosion.
- When earth is hit by a meteor.
Describe some of the precautions which are intended to safeguard people’s life and property against lightning.
Precautions which are intended to safeguard people’s life and property against lightning are :
- Use of open vehicles like motorcycles, tractors etc. should be avoided.
- Do not carry umbrella during thunderstorms.
- If in a forest, take shelter under shorter trees.
- If no shelter is available, we should stay far from tall trees, poles or other metal objects. We should squat low to the ground.
B. Inside the house
- During a thunderstorm, we should avoid contact with telephone cords, electrical wires and metal pipes.
- Bathing should be avoided during thunderstorms to avoid contact with running water.
- Electrical appliances like computers, T.V., A.C., etc. should be unplugged. Electrical lights remaining on do not cause any harm.
Multiple Choice Questions (MCQs)
1. Take a used ballpen refill and rub it vigorously with a piece of polythene. Which of the following observation is incorrect if you bring it close to small. pieces of paper, dry leaf, husk or mustard seed?
(a) The ball pen refill attracts small pieces of paper and dry leaf.
(b) The ball pen refill attracts husk and mustard seeds.
(c) The ball pen refill acquires a small electric charge.
(d) The polythene is not charged at all.
(d) The polythene is not charged at all.
2. When a plastic comb is rubbed with dry hair
(a) It acquires a small charge.
(b) It does not acquire any charge.
(c) Both the comb and the hair acquire a charge.
(d) The bristles of the comb break.
(a) It acquires a small charge.