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• Behaviour of charged:
  • Like charges repel each other
  • Unlike charges attract each other
• Polarity: Property that differentiate between two kinds of charges
• Charges by conventions –
  

  Object	Charge
  Glass rod	Positive
  Cat’s fur	Positive
  Plastic rod	Negative
  Silk	Negative

• Gold leaf apparatus is used to detect charge on the body
• Working of gold leaf apparatus:
  • When charged body touches the metallic top of gold leaf electroscope, leaves of electroscope diverges. Here metallic leaves gets charged.
  • The extent of divergence suggest amount of charge in the body.
  • If you touch the top again, the charges flow from your body to the earth, thereby causing convergence. Thus metallic leaves get discharged.

Click here to watch video on Working of Gold Leaf Apparatus

• Earthing: Process of transferring charge from charged object to the earth
• How is lightning produced?
  • During a thunderstorm, air current move upward and water droplets move downwards simultaneously.
  • Due to rubbing action between them electric charges separates, positive charges collects at the top of cloud and negative charge at the bottom.
  • When stored charge becomes very large, air in between fails to resist the flow
  • Thus positive and negative charges meet producing bright flash with sound.
  • This is called lightning

  Click here to watch video on How Is Lightning Produced?

• Do’s and don’ts during thunderstorm:
  • Avoid travelling in cars, motorbikes, tractors or any open vehicle
  • Open fields, playgrounds, tall trees, etc are not safe
  • Stay away from metal objects
  • Should sit in squat position, this provides smaller surface area, therefore has low risk of lightning to strike
  • Stay away from telephone cords, electric wires and metal pipes at home
  • Use of mobile phones is safe
  • Avoid bathing or contact with running water
  • Unplug electrical appliances at home
  • For protection of buildings install metallic rod which provides earthing.
• Earthquake: Sudden shaking and trembling of earth’s surface. Watch video on how earthquake is caused here.
• Seismic waves: Waves produce on the earth’s surface due to earthquake
• Seismograph: Instrument used to record seismic waves
• Power of earthquake is measured in terms of Richters scale
• Seismic zones or fault zones: Weak zones where chances of earthquake is maximum. Some seismic zones in India
  • Kashmir
  • Western and Central Himalayas
  • Whole of North-East
  • Rann of Kutch
  • Rajasthan
  • Indo – Gangetic Plain
  • Some areas of south India
• Prevention against earthquakes
  • Construct building and houses quake safe
  • If earthquake strikes take shelter under the table till shaking stops
  • Stay away from tall heavy objects
  • In bed protect yourself with pillow
  • If you are outdoor find clear spot away from buildings
  • While driving or inside car or bus, ask to drive slowly towards the clear spot