NCERT Solutions Class 8th Science Chapter – 12 Some Natural Phenomena Notes

NCERT Solutions Class 8th Science Chapter – 12 Some Natural Phenomena

TextbookNCERT
Class 8th
Subject Science
Chapter12th
Chapter NameSome Natural Phenomena
CategoryClass 8th Science
Medium English
SourceLast Doubt

NCERT Solutions Class 8th Science Chapter – 12 Some Natural Phenomena 

Chapter – 15

Some Natural Phenomena

Notes

Static Electricity

• The chemical charge generated by rubbing is called static electricity because these charges do not transmit.

• There are two types of charges-positive charge and negative charge.

• When we rub two objects, made of different substances, together the charge they acquire are opposite to each other.

Electric Current – When charges move they constitute an electric current.
Earthing 

•  The process of transfer of charges from a charged object to the Earth is called earthing.

• Earthing is provided in electrical wiring in building to protect us from electrical shocks, in case of any leakage of electrical current.

• 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 cam 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.

• 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.

Crust – Crust is the uppermost layer of Earth’s surface (8 km – 32 km).
Electric discharge – When negative charges from the clouds and positive charges on the ground meet, a huge amount of energy is produced as bright light and sound, which we see as lightning. The process is called electric discharge.
Earth’s Plates – The outermost layer of the earth is not in one piece. It is fragmented. Each fragment is called a plate.
Earthquake – An earthquake is a sudden shaking or trembling of the Earth. It is caused by a disturbance deep inside the earth’s crust (i.e., by the movement of Earth’s plates).
Electroscope – Electroscope is a device used to test whether an object is carrying charge or not.
Lightning – The process of electric discharge between clouds and the Earth or between different clouds causes lightning.
Lightning Rod – Lightning rod is a device used to secure tall buildings from the effect of lightning conductor. A metallic rod taller than the height of the building is installed in the walls of the building during its construction to protect it from the effect of lightning.
Negative Charge – When the charge of an object is due to the excess of electrons, it is called a negative charge.
Positive Charge – When the charge of an object is due to the loss of electrons, it is called a positive charge.
Richter Scale – The power of an earthquake is expressed in terms of magnitudes on a scale called the Richter Scale.
Seismograph – The seismic waves are recorded by an instrument in the form of a graph called the seismograph.
Thunder – The loud noise which accompanies lightning.
Thunderstorm – A storm accompanied by thunder and lightning.
Transfer of Charge – Electrical charge can be transferred from a charged object to another through a metal conductor.
Tsunami – Earthquakes may cause tsunamis in oceans, resulting in huge damage in coastal areas.
Tremor – Trembling or shaking of the Earth.

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