Key Points - Some Natural Phenomena

- 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 strike 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 know as fault zones.
- 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.
- We should take necessary precautions to protect ourselves from earthquakes.
- Richter Scale: A logarithmic scale, ranging from 1 to 10 for indicating the intensity of an earthquake.
- Seismic Waves: The energy released at the focus of an earthquake, propagates outwardly.
- Seismograph: An instrument by which seismic waves of an earthquake are monitored.
- Epicentre: A point on the earth above the seismic force.
- Fault Zones: Earthquake prone areas in the earth’s crust.