Current Affairs 8th Class

Category : 8th Class

Solar System and Some Natural Phenomenon

Solar System

Solar system, the sun and everything that orbits the sun, including the planets and their satellites, the dwarf plants, asteroids, kuiper belt objects and comets.

Solar System

Sun

Sun is the closest star to the earth. Its average distance from the earth is about 150 million kilometres. It consists mainly of hydrogen and helium. Diameter of sun is about

1.4 million km. The temperature at its surface is about\[{{6000}^{o}}C\].

Planets

Based on the distances of planets from the sun they are as follows: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. All the planets revolve around the sun in a fixed path called orbit. Planets which are close to the sun like Mercury, Venus, Earth and Mars are called inner planets or terrestrial planets. Jupiter, Saturn, Uranus and Neptune are known as the outer planets or jovian planets as they are far from the sun.

Mercury - is nearest to the sun. This planet has a rocky surface which is covered with craters. It is the smallest planet of the solar system.

Venus - is the second planet from the sun. Venus is a rocky planet. It is the hottest planets as its atmosphere is mainly made up of carbon dioxide. It rotates on its axis from east to west.

Earth - is the third planet from the sun. Earth's atmosphere has sufficient oxygen, the gas we need to live and water.

Mars - is also known as a red planet. The thin atmosphere of mars contains mainly carbon dioxide with small amounts of nitrogen, oxygen, noble gases and water vapour. It appears red due to the high amount of iron oxide present on its surface.

Jupiter - is the biggest planet and is made mainly of hydrogen and helium.

Saturn - is the second biggest planet of the solar system and is made up of mainly hydrogen and helium. It has well developed system of rings surrounding it. It is the least dense planet and can float in water.

Uranus - is the third biggest planet of the solar system and is mainly made up of hydrogen and helium.

Neptune - is the outermost planet of the solar system and is made mainly of liquid and frozen hydrogen and helium gases.

The Moon

A celestial body that revolves around a planet is known as natural satellite or moon of the planet. The earth has only one moon. It reflects the light of the sun. Its surface is covered with craters and mountains.

Phases of moon

Shapes of the bright part of the moon, as seen from the earth, are known as the phases of moon.

Constellations

Are group of stars which appear to form some recognizable shape or pattern. Some constellations are:

Ursa Major, Cassiopeia, Orion, Leo Major, etc.

Electric Charge

Electric charge is a property of certain subatomic particles like electrons and protons that allows them to attract or repel other charged particles by electric force. This is the force which binds nucleus and electrons of an atom together.

Types of Charges

(i) Negative charge

(ii) Positive charge

Like charged particles repel each other whereas unlike charged particles attract each other. Electrons are negatively charged particles whereas protons are positively charged particles. That i-s why between two electrons force of repulsion is experienced whereas between an electron and a proton, force of attraction is experienced.

An Object can be charged by the Following Ways

(i) Charging by rubbing (friction)

(ii) Charging by induction

(iii) Charging by conduction

Electroscope

An electroscope is an instrument for detecting the presence of electric charge on an object. It consists of two thin metal leaves suspended from a metal hook. When the hook is brought near a source of electric charge, some of the electrons in the hook are pushed to the leaves (if the source is negative) or pulled up to the hook from the leaves

(if the source is positive). Due to this the two metal leaves repel each other. This shows the presence of charge on the body.

Lightning

            Lightning is natural phenomena. The bright flash of light which we see in the clouds is called lightning.

Lightning is an electric current. Within a cloud many small bits of ice bump into each other as they move around in the air. Due to these collisions electric charges are produced. The positive charges form at the top of the cloud and the negative charges form at the bottom of the cloud. When the amount of these charges becomes extremely large, then the electric charges start flowing with high speed through air between them as a result an intense spark of electricity is produced in the sky.

Earthquake

Earthquake is a destructive natural phenomenon which occurs due to sudden movements in earth' crust. The shaking of the ground caused by sudden movements in earth's crust is known as earthquake. Earthquake sometimes causing great destruction. The intensity of an earthquake is measured by Richter scale. The place inside the earth's crust where the earthquake is generated is known as focus of the earthquake. The point on the earth's surface directly above the focus is called epicentre. The waves generated by an earthquake are called the seismic waves. The instrument which is used to measure and record the magnitude of an earthquake in terms of shockwaves is known as seismograph.