PSEB 8th Class Science Notes Chapter 15 Some Natural Phenomena

This PSEB 8th Class Science Notes Chapter 15 Some Natural Phenomena will help you in revision during exams.

PSEB 8th Class Science Notes Chapter 15 Some Natural Phenomena

→ Sparks, in the sky, was believed to be the wrath of God.

→ In 1752, Benjamin Franklin established that lightning and the spark of amber were the same things.

→ Electricity is responsible for sparks or lightning in the sky.

→ Rubbing produces electric charges in some materials.

→ Similar materials acquire the same charges when rubbed with the same materials.

PSEB 8th Class Science Notes Chapter 15 Some Natural Phenomena

→ Like charges repel each other.

→ Different materials acquire different charges when rubbed with the same materials or different materials.

→ Unlike charges attract each other.

→ Two kinds of changes are positive and negative.

→ The electric charge generated by rubbing is called static electricity.

→ Static charges are stationary i.e. they do not move.

→ Moving charge constitutes an electric current.

→ Earthing is the process of transfer of charges from a charged object to the earth. Lightning is nothing but an electric discharge.

→ Electric discharge occurs when

  • two clouds come together
  • clouds come near the earth surface
  • clouds and the human body come closer

→ Clouds carry -ve charges on them and on coming in contact with +ve charge produce a huge amount of energy in form of bright light and sound.

→ A house or a building and even a closed vehicle is the safest place during a thunderstorm.

→ A lightning conductor is a device to secure tall buildings from the effect of lightning.

PSEB 8th Class Science Notes Chapter 15 Some Natural Phenomena

→ Electric cell emits electric discharge, which can be up to 650 volts.

→ Thunderstorms, cyclones, lightning are natural phenomena that cause large-scale destruction of human life and property.

→ Earthquake is also a natural phenomenon.

→ Predictions about thunderstorms, cyclones, and lightning can be done, but earthquakes can not be predicted.

→ An earthquake is the sudden shaking or trembling of the earth.

→ Floods, Landslides, Tsunami are caused by earthquakes.

→ A seismograph is an instrument meant to record seismic waves produced on the surface of the earth by tremors.

→ The intensity of an earthquake is measured in terms of magnitudes on a scale called the Richter Scale.

→ Symmetrical and mud/timber buildings are to be constructed in seismic-prone areas.

→ Static Electricity: The electrical charge excited by rubbing is said to be static electricity.

→ Earthing: The process of transfer of charges from a charged body to the earth is called earthing.

→ Electric Discharge: The process of producing light and sound by clouds is called electric discharge.

→ Thunderstorm: A loud noise produced across the sky during a rainy day is called a thunderstorm.

PSEB 8th Class Science Notes Chapter 15 Some Natural Phenomena

→ Lightning: A bright light produced across the sky, due to the rubbing of two clouds or clouds and earth, is lightning.

→ Earthquake: The disturbance deep inside the earth’s crust that causes trembling and shaking of the earth, is called an earthquake.

→ Lightning Rod: It is a device to secure tall buildings from the effect of lightning.

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