# AP Board 8th Class Physical Science Important Questions Chapter 11 Some Natural Phenomena

AP State Syllabus AP Board 8th Class Physical Science Important Questions Chapter 11 Some Natural Phenomena

## AP State Syllabus 8th Class Physical Science Important Questions 11th Lesson Some Natural Phenomena

### 8th Class Physical Science 11th Lesson Some Natural Phenomena 1 Mark Important Questions and Answers

Question 1.
What is an electroscope?
The device which can be used to test whether an object is carrying charge or not is called electroscope.

Question 2.
What is electrical discharge? Where does electrical discharge takes place?
The process of transfer of negative or positive charges is called electrical discharge.
The electrical discharge can occur between two or more clouds, or between clouds and the earth.

Question 3.
What is the other device at buildings acts as lightning conductor?
The metal columns used during construction and water pipes in the buildings also protect us by acting as lightning conductors.

Question 4.
Why water pipes should not be touched during thunder storm?
Answer: During thunder storm there would be a possibility that the charge developed due to lightning may travel through the water pipes. So we should not touch water pipes during thunder storm in order to avoid electric shocks.

Question 5.
What is an earthquake?
An earthquake is a sudden shaking or trembling of the earth lasting for a short period of time due to disturbance deep inside the earth’s crust.

Question 6.
What is the cause of most earthquakes?
The most earthquakes are caused by the movement of earth’s plates.

Question 7.
What is a earth’s plate?
The outer most layer of the earth is not in one piece. It is fragmented. Each frament is called a earth’s plate.

Question 8.
How do we measure the intensity of the earthquake?
The power of an earthquake is expressed in terms of a magnitude on ricter scale.

Question 9.
What is the range of destructive earthquake?
The destructive earthquake have magnitude heigher than 7 on the ricter scale.

Question 10.
Whether it is possible to predict when and where the next earthquake might occur?
It is not possible to predict when and where the next earthquake might occur. But we can predict that there is a possibility of the earthquake when a volcano erupts, or a meteor hits the earth, or an underground nuclear explosion takes place.

Question 11.
What are seismic waves?
The tremors produce waves on the surface of the earth. These are called seismic waves.

Question 12.
What are the places in Andhra Pradesh which lie in seismic zone?
According to seismic hazard map Andhra Pradesh lies in zones II and III. The south eastern districts of Chittoor, YSR Kadapa, Nellore and Krishna and Godavari delta region have been placed in zone III and the city of Hyderabd lies in zone II.

### 8th Class Physical Science 11th Lesson Some Natural Phenomena 2 Marks Important Questions and Answers

Question 1.
What is earthing? Why does earthing is provided in buildings?

1. The process of transferring of charge from a charged object to the earth is called earthing.
2. Earthing is provided in building to protect us from electrical shock due to any leakage of electric charge.

Question 2.
Which is safe place during thunder storm?

1. A house or building of low height.
2. If you are travelling in a bus or in a car, you are safe inside provided that doors and windows are closed.
3. If you are in a forest taking shelter under shorter trees than a taller tree is a good idea during the thunder storm.

Question 3.
What are different layers of earth? Draw a neat diagram of different layers of earth and label its parts?

The different layers of earth are:

1. Crust: This is upper most layer of the earth.
2. Mantle: This is middle layer.
3. Core: This is inner layer of the earth.

Again core is divided into two parts.

1. Inner core
2. Outer core

Question 4.
How does earthquake is formed?
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.
When they brush past on one another, or a plate goes under another plate due to collision, they cause disturbance in the earth’s crust. It is this disturbance that shows up an earthquake on the surface of the earth.

Question 5.
What are the main instruments used by seismologists ? What are the uses of those instruments?
Seismologists use two main devices to measure an earthquake.

1. Seismograph: The seismograph is an instrument that measures the seismic waves caused by an earthquake.
2. Seismoscope: The seismoscope is an instrument that measures the occurrence or the time of occurrence of an earthquake. The seismoscope is a simple device which can be used without any technological background.

Question 6.
How does destructive energy related to ricter scale?
Ricter scale is not linear. This means that an earthquake of magnitude 6 does not have one and half time of the destructive energy of an earthquake of magnitude 4.
In fact, an increase of 2 in magnitude means 1000 times more destructive energy. For example, an earthquake of magnitude 6 has thousand times more destructive energy than an earthquake of magnitude 4.

Question 7.
Which scale measures the destructive energy released by earth more accurately?
The moment magnitude scale which is based on the amount of displacement that occurred along a fault zone rather than the measurement of ground motion at a given point measures more accurately the energy released by earthquake than the ricter scale.
It is the only magnitude scale that adequately measures the size of large earthquake.

Question 8.
Raju watched pictures of earthquake victims on T.V. What are the questions raised in his mind about earthquake ?

1. What is the cause of earthquake?
2. Why some areas are frequently affected by earthquakes?
3. What are the indications before a major earthquake takes place?
4. What are the precautionary method to be followed to avoid excess of loss of human life?
5. What are the measures we have to take when earthquake occur?

Question 9.
Which places are not safe during a thunderstorm?

1. Travelling in an open place.
2. Standing under tall trees in open fields or in a garden/park.
3. Staying in multi storied building which do not have lightning conductors.
4. Standing near electric poles or telephone poles.
5. Speaking on landline telephones.
6. Using electrical appliances like TV and computer.

Question 10.
Explain how do you determine the intensity of Earthquake.

1. The intensity of Earthquake can be measured on richter scale. Like many other scales, richter scale is not linear. That means increase of 2 in magnitude mean 1000 times more destructive energy.
2. There is another method of measuring the intensity of earthquake using the moment magnitude scale which is based on the amount of displacement that occurred along a faulty zone.
3. The moment magnitude measures energy released by the earthquake more accurately than the richter scale. It is the only magnitude scale that adequately measures the size of large earthquakes.

Question 11.
Is there any alternative methods to find the intensity of earthquake ?
The main method to find the intensity of earthquake is richter scale.
The alternative methods are:

1. The moment magnitude scale: Which is based on amount of displacement that occured along a faulty zone.
2. Mercalli scale: This scale uses the observations of the people who experienced the earthquake to estimate intensity.

Question 12.
We know that the clouds have charges. Can we produce current through these charges?
Cloud to ground lightning discharges 30,000 amperes and up to 100 million volts and emits light, X rays, radio waves and even gamma rays.
Plasma temperature in lightning can approach 28000 K and electron densities may exceed 1024/m3.
So it not easy to use this charge as electricity.

Question 13.
What happens if two objects having same charge brought close to each other?
What happens if two objects having different charges are brought close? Can you give an example for this?
Two objects having same charge repel each other and two objects having different charge attract each other.
e.g.: A balloon rubbed with woollen cloth is repelled by another balloon rubbed with woollen cloth because both will acquire same type of charge.
A balloon rubbed with a woollen cloth is attracted by a refill rubbed with a polythene sheet because both will acquire different type of charge.

Question 14.
How do you relate the energy release during the collusion of fault lines during earthquake to the atmospheric variation on the surface of the earth?
An earthquake affects the atmosphere by creating amounts of debris and dust which will add to the air that we breathe. Earthquakes can also trigger volcanoes which will release tonnes of ashes and other debris into the atmosphere. This can sometimes cause the blocking out of the sun, air pollution and are increased amount of carbon in the air.

Question 15.
Explain why a charged ballon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?

1. We have seen that two balloons with similar charges on them, whether positive or negative, repel each other. Similarly two balloons with dissimilar charge on them attract each other.
2. So, similar charges repel each other while dissimilar charges attract each other.

### 8th Class Physical Science 11th Lesson Some Natural Phenomena 4 Marks Important Questions and Answers

Question 1.
Explain how lightning would be formed?
The clouds moving in air acquire a charge on their surface due to the friction with particles of air. As the surface area of a cloud is very large, the amount of charge accumulated on its surface is very high.
When a charged cloud comes close to another cloud is induces an opposite charge on the later and the accumulated charge tries to move from one cloud to another cloud.
But the air present between them bring a poor conductors of electricity resists the flow of charge between them.
When the magnitude of the accumulated charges become very large, the air which is normally a poor conductor of electricity, is no longer to able to resist their flow.
Hence discharge takes place between negative and positive charges which produce streaks of bright light and sound. We see streaks as lightning.

Question 2.
Which is not safe during a thunder storm?

1. Travelling in an open place.
2. Standing under tall trees in open fields or in a garden/park.
3. Staying in multi storied building which do not have lightning conductors.
4. Standing near electric poles or telephone poles.
5. Speaking on landline telephones.
6. Using electrical appliances like T.V. and Computer.

Question 3.
What is a lightning conductor ? How does it works during lightning ?
Lightning conductor is a device used to protect buildings from the effect of lightning. A metallic rod, taller than 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 other is buried deep in the ground. The rod provides an easy route for the transfer of electric charge to the ground.
The projected end of the metal rod is at a height more than the height of the building. Hence it receives the charge first during lightning because it is closer to the cloud than the building.
As it is good conductor of electricity, it allows all the charge to flow through it there by causing no damage to the buildings.

Question 4.
What are seismic zones? Name main seismic zones in India.
Earthquakes are caused by the movement of plates, the places at boundaries of the plates are considered as weak zones where earthquakes are more likely to occur. These weak zones are also called as seismic or fault zones.
The main seismic zones in India are Kashmir, Western and Central Himalayas, the whole of North east, Rann of Kutch, Rajasthan, Indogangetic plane and some areas of South India.

Question 5.
Draw a table showing magnitude ricter scale reading and effect of earthquake for that reading?

 Ricter Magnitude Earthquake effects less than 3.5 Generally not felt, but recorded 3.5 to 5.4 Often felt, but rarely cause damage 5.5 to 6.0 At most slight damage to well designed buildings can cause major damage to poorly constructed buildings over small regions. 6.1 to 6.9 Can be destructive in areas upto 100 kilometres across where people live. 7.0 to 7.9 Major earthquake. Can cause serious damage over larger areas. 8 or greater Great earthquake can cause serious damage in areas several hundred kilometers across.

Question 6.
How do you appreciate the efforts of the scientists to develop a Lightning conductor to protect buildings from the effect of lightning?
Lightning conductor is a device used to protect buildings from the effect of lightning.
A metallic rod, taller than 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 other is buried deep in the ground. The rod provides an easy route for the transfer of electric charge to the ground.
The projected end pf the metal rod is at a height more than the height of the building. Hence it receives the charge first during lightning because it is closer to the cloud than the building.
As it is good conductor of electricity, it allows all the charge to flow through it there by causing no damage to the buildings. Hence sole of scientists is appreciated.

Question 7.
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.
In India National Disaster Force provides relief for disaster victims.
Problems of earthquake victims:

1. Death: Many times, the people who support a family socially and economically dies. This causes most of the other members of the family to either fight their way through, or restart their lives from the bottom of the food chain.
2. Destroyed Structures: If the members of the family survive, then they could still be short of a home. The earthquake would have caused the destruction of their house and because of that, they would be left homeless.
3. No food or water: In the aftermath of an earthquake, people see weather all the pipelines, roads, etc. are in good shape or order. If the pipes are broken, then water scarcity begins. If the roads are broken, then food supplies cannot be transported, later causing problems in food scarcity.
4. Electricity: With inadequate supply of electricity, the debris and rubble will take a lot of time and if people are under it then they may die before the rubble is removed.
5. Spread of diseases: After the destruction of many buildings, the sewer pipes will also break and open, causing spread of diseases everywhere.

Help rendered by relief organisation:

1. They minimize the death of people.
2. They provide drinking water and food for victims.
3. They provide shelter for earthquake victims.
4. They provide medical facility for earthquake victims.

Question 8.
Explain how lightning would be formed.
The clouds moving in air acquire a charge on their surface due to the friction with particles of air. As the surface area of a cloud is very large, the amount of charge accumulated on its surface is very high.
When a charged cloud comes close to another cloud is induces an opposite charge on the later and the accumulated charge tries to move from one cloud to another cloud.
But the air present between them bring a poor conductors of electricity resists the flow of charge between them.
When the magnitude of the accumulated charges become very large, the air which is normally a poor conductor of electricity, is no longer to able to resist their flow.
Hence discharge takes place between negative and positive charges which produce streaks of bright light and sound. We see streaks as lightning.

Question 9.
How the power of earthquake estimated? At what strength it becomes destructive?

1. The power of earthquake is expressed in terms of magnitude on scale called Richter scale.
2. The destructive earthquakes have magnitudes higher than about 7 on richter scale.
3. Like many other scales, richter scale is not linear. It means that earthquake of magnitude 6 does not have the twice the destructive energy of an earthquake magnitude 3.
4. Infact, an increase of 2 in magnitude means 1000 times more destructive energy.
5. For example, an earthquake of magnitude 6 has thousand times more energy than earthquake of magnitude 4.

Question 10.
What suggestions will you give to people living in seismic areas so that the destruction due to earthquake may be minimized?

1. We know that earthquakes cannot be predicted and that they can be highly destructive.
2. It is therefore important that we have to take necessary precautions to protect ourselves all the time.
3. Consult qualified architect and structural engineer to build the buildings.
4. It is better to fix the cup boards and shelves to the walls, so that they do not fall easily.
5. Be careful where you hang wall clocks, photoframes, water heaters, etc. so that in the event of an earthquake they do not fall on the people.
6. Some buildings may catch fire due to an earthquake, it is necessary that all buildings have fire fighting equipment installed.

### 8th Class Physical Science 11th Lesson Some Natural Phenomena Important Questions and Answers

Question 1.
Draw a neat diagram of the instrument used to measure the intensity of earthquake. Name the scale used in this instrument.

Richter scale is used in this instrument.

Question 2.
“Earthquakes can cause floods, landslides and tsunamis. A major tsunami occurred in the Indian ocean on 26th December 2004. All the coastal areas around the ocean, suffered huge losses.”
Based on the above information answer the following questions:
i) What is the cause for tsunami?
Tsunami is caused by sudden movement of the earth that happens under the sea.

ii) What happens when a major tsunami occurs?
When tsunami waves become extremely large in height, they .savagely attack coast lines, causing devastating property damage and loss of life.

iii) Name the instrument which is used to detect an earthquake and what are its major parts.