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The chapter discusses two destructive natural phenomena: lightning and earthquakes, and highlights the precautions we can take to minimize their destructive effects. It explains the science behind lightning, including the process of charge accumulation and discharge, as well as the unpredictable nature of earthquakes and their severe consequences on human life and property.
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What we have learnt
- Some objects can be charged...
- There are two kinds of char...
- Like charges repel and unli...
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What we have learnt
- Some objects can be charged by rubbing with other objects.
- There are two kinds of charges — positive charge and negative charge.
- Like charges repel and unlike charges attract each other.
- The electrical charges produced by rubbing are called static charges.
- When charges move, they constitute an electric current.
- An electroscope may be used to detect whether a body is charged or not.
- The process of transfer of charge from a charged object to the earth is called earthing.
- The process of electric discharge between clouds and the earth or between different clouds causes lightning.
- Lightning strikes could destroy life and property.
- Lightning conductors can protect buildings from the effects of lightning.
- An earthquake is a sudden shaking or trembling of the earth.
- Earthquake is caused by a disturbance deep inside the earth’s crust.
- It is not possible to predict the occurrence of an earthquake.
- Earthquakes tend to occur at the boundaries of earth’s plates. These boundaries are known as fault zones.
- The destructive energy of an earthquake is measured on the Richter scale. The earthquake measuring 7 or more on the Richter scale can cause severe damage to life and property.
- We should take necessary precautions to protect ourselves from earthquakes.
Key Concepts
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Term: Static Charge
Definition: Electrical charges produced by rubbing are called static charges, which do not move by themselves.
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Term: Lightning
Definition: Lightning is an electric discharge that occurs when accumulated charges in clouds overcome the insulating properties of air.
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Term: Earthquake
Definition: An earthquake is a sudden shaking or trembling of the earth caused by disturbances deep inside the earth's crust.
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Term: Electroscope
Definition: An electroscope is a device used to detect electrical charge by observing the behavior of metal foil strips.
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Term: Richter Scale
Definition: The Richter scale measures the magnitude of earthquakes, indicating the amount of energy released.