Some Natural Phenomena

Electroscope is a device that can be used to test whether an object is carrying charge or not.

i. In an electroscope, there are some strips (leaves) which carry similar charges.

ii. Similar charges repel each other and as a result, they become wide open.

iii. This shows that the object carries a charge.

Electrical charge can be transferred from a charged body to another through a metal conductor. Among the given options, copper wire is a metal conductor.

Earthquake is caused by a disturbance deep inside the earth’s crust. The movement of the earth’s plates causes earthquakes. It lasts for a very short time. It occurs all over the earth.

When two charged objects are brought close to each other, they may attract or repel depending on the types of charges they carry:

i. Like charges repel each other.

ii. Unlike charges attract each other.

Tsunami is a natural phenomenon in which sea waves are produced due to the disturbance under the sea.

i. A major nuclear explosion under sea, earthquake or volcanic eruption can cause tsunami.

ii. Lightning is another thing. It is caused by the accumulation of charges in clouds.

iii. Negative and positive charges meet which produces streaks of bright light.

iv. We see streaks as lightning.

Earthquake:

i. It is a sudden shaking or trembling of the earth.

ii. It lasts for a very short minute.

iii. It is caused by a disturbance deep inside the crust of the earth.

Earthquakes are caused by the movement of plates.

i. The boundaries of the plates are the weak zones.

ii. Weak zones are the zones where earthquakes are most likely to occur.

iii. The weak zones are also known as seismic zones or fault zones.

The outermost layer of the earth is called crust. Earthquake is caused by the disturbance deep down inside the earth’s crust.

In India, the areas in which earthquakes are more likely to occur are North-east India, Rann of Kutch and Rajasthan. On the other hand, earthquakes are less likely to occur in Orissa.

Earthquake can cause floods, landslides and tsunamis. There can be a great loss to life and property. But lightning is an another thing. It is caused by the accumulation of charges in the clouds.

(a) True

Earthquakes occur all the time, all over the world.

i. They are not even noticed.

ii. Most earthquakes are much less frequent.

iii. They can cause a lot of damage to life and property.

Hence, the given statement is true.

(b) True

The plates of the outermost layer of the earth are always in continuous motion. The collision between the plates causes a disturbance in the earth’s crust.

(c) True

Tremors are caused by the disturbance deep down inside the uppermost layer of the earth called crust.

i. Tremors can also be caused by the eruption of a volcano.

ii. The eruption of a volcano causes a disturbance in the earth’s crust.

Hence, the given statement is true.

(d) False

The process of electric discharge occurs between two or more clouds or between clouds and earth. This leads to lightning. Lightning is caused by the accumulation of charges in the clouds.

Hence, the given statement is false.

(e) True

Bathing outdoors should be avoided during thunderstorms to avoid contact with running water otherwise the thunderstorm strike can bring electric shock and can destroy life.

No, it is not possible to predict the occurrence of an earthquake.

i. We know for sure what causes an earthquake.

ii. But, it is not yet possible to predict when and where the next earthquake might occur.

iii. Scientists are trying hard to predict the occurrence of earthquake.

If a charged plastic straw is brought near another uncharged plastic straw, they will attract each other. Because we know that unlike (opposite) charges attract each other.

If aluminum (metal) strips in an electroscope are replaced by plastic strips, the strips won’t spread out. As a result, we cannot test whether the object is carrying a charge or not.

Note: Electric charge can be transferred from a charged object to another only through a metal conductor.

When plastic straws A and B are rubbed with a dry cotton cloth and brought near each other, they will repel each other because both will gain the similar charge. Similar charges repel each other.

No, the lightning conductor will not work, if it is left hanging in the air by mistake because:

i. The charge will pass only when the lightning conductor is connected to the earth by using any metal plate.

ii. It is given that the lightning conductor was left hanging in the air, hence no charge will pass.

iii. As a result, the lightning conductor will not be effective anymore.

No, lightning will not occur because:

i. The separation of charges cannot take place in conductors.

ii. If air and cloud are good conductors of electricity, then all the charges collected at the clouds will transfer to the air.

iii. Therefore, the accumulation of charges on the clouds cannot take place.

iv. Hence, lightning will not occur.

A is lightning conductor and B is copper plate.

i. A lightning conductor is a device used to protect the building from lightning effects.

ii. It is a long metallic rod taller than building installed on the walls of the building.

iii. One end of the rod is kept out in the air and other is buried deep in the ground connected with a copper plate.

iv. The rod provides an easy route for the transfer of electric charge to the ground.

No, lightning will not strike the building because:

i. The charge separation cannot take place in conductors.

ii. The lightning falling on the building will remain on the surface of the building.

iii. Therefore, it will not strike the building.

No, there is no need to install the lightning conductor in the building because

i. The conducting material will act as a lightning conductor itself.

ii. It will protect the building from the effect of lightning.

It happens because:

i. The television screen or computer monitor are fully charged.

ii. The charge gets accumulated (stored) on the screen.

iii. When we touch the screen with our hands which are uncharged, the charges transfer from the screen (discharges) through our hands.

iv. As a result, we get a slight shock.

Lightning conductor:

i. It is a device used to protect the building from lightning effects.

ii. It is a long metallic rod taller than building installed on the walls of the building.

iii. One end of the rod is kept out in the air and other is buried deep in the ground connected with a copper plate.

iv. The rod provides an easy route for the transfer of electric charge to the ground.

v. That’s how lightning conductor protects a building from getting struck by lightning.

If another charged object carrying an equal amount of positive charge is brought in contact with the clip:

i. The negative charge which was given to the clip earlier will be neutralized.

ii. Neutral charges will take place.

iii. As a result, the diverged strips will collapse.

Note: When a number of positive and negative charges become equal, they cancel out each other. As a result, overall charge becomes zero which is called a neutral charge (neither positive nor negative)

The strips will come back to the original state because:

i. When we touch the strip with our hand, the charge on the electroscope strips will transfer from our hand to the ground.

ii. Or we can say that strips will get discharged through our hand to the ground.

iii. As a result, the strips will contract and come back to its original state.

i. During the development of a thunderstorm, the air current moves upward and the water droplets move downward.

ii. These movements of air and water droplets cause charge separation.

iii. The positive charges collect at the upper edges of the clouds.

iv. The negative charges collect at the lower edges of the clouds.

v. There is an accumulation of positive charges near the ground also.

vi. When the magnitude of the charges become too large, negative and positive charges meet.

vii. This produces streaks of bright light and sound.

viii. Hence, lightning causes by the accumulation of charges on the clouds.

If an earthquake strikes when we are inside the house, we should take three following precautions to protect ourselves are:

i. If we are in a bed, we should not get up. We should protect our head with a pillow.

ii. We should not go near the tall and heavy objects that may fall on us. Pick a safe place as soon as possible.

iii. We should take shelter under a table and stay there until earthquake stops.

It is safer to use a wireless telephone instead of a landline telephone during lightning because:

i. Lightning can strike electrical wires, telephone cords or metal pipes because lightning is an electrical discharge.

ii. If the lightning strikes any of these, it can destroy one’s life and property.

iii. During a thunderstorm, contact with these should be avoided.

iv. Hence, it is safer to use mobile phone and cordless phones.

The following precautions we should take if lightning occurs while we are outside the house:

i. We should not carry an umbrella during thunderstorms.

ii. We should stay far away from trees.

iii. We should stay away from any fountain, pond or any other water bodies.

iv. We should stay far away from poles or any metal objects. They are too dangerous.

v. We should not lie on the ground. Sit down and place our hands on our knees with our head between the hands. This position will avoid us from the effect of lightning.

vi. We should not go near the open motorbikes, cars, tractors etc. They are not safe at all.

No, there will not be any effect on aluminum strips because:

i. Ebonite rod is an insulator. It does not carry a charge at all.

ii. Therefore, the charged body which is brought in contact with the ebonite rod, will not transfer charges to the ebonite rod.

iii. As a result, there will be no charge on the aluminum strips.

iv. Hence, no repulsion of the aluminium strips will occur.