Definition : Simple machines are tools which makes our work easier and faster Examples of simple machines are- Lever it is a rod or bar supported by fulcrum and effort. It reduces the the force by a push or a pull. Pulley is a small wheel with grooves around its outer edge. A pulley together with a chain or a rope is used to lift . . .
The flow of electric current in any circuit causes electric energy. Like, an electric bulb converts electrical energy into light energy, Electric fan converts electric energy into mechanical energy, Radio set converts electrical energy into sound energy. Electrical energy: We know that work done in flowing the charge q through a conductor having p . . .
For convenience live, neutral and earth wire are provided with different colours. According to old convention of colour coding, live wire is red, neutral wire is black and earth wire is green in colour. How-ever in new international convention the respective colours for three wires are brown, light blue and green. . . .
The human eye is one of the most valuable and sensitive sense organs. It enables us to see the wonderful world and the colours around us. On closing the eyes, we can identify objects to some extent by their smell, taste, sound they make or by touch. It is, however to impossible to identify colours while closing the eyes. Thus, of all the sense organs, t . . .
Real image Virtual image A real image is formed due to actual intersection of the reflected rays. A virtual image is formed when the reflected rays meet if they are produced backwards. A real image can be obtained on a screen. A virtual image cannot be . . .
Concave mirror Convex mirror It is made by silvering the outer surface of a part of the hollow sphere, so reflection takes place from the inner surface. It is made by silvering the inner surface of a part of the hollow sphere, so reflection takes place from the bul . . .
Usually a cable with three-pin plug at its one end is provided with any electrical appliances that connects it to the power supply. This plug is inserted into a three-holes socket fixed on a wooden or insulating power supply board. The bigger hole on top of the socket is connected to earth wire, right hole to the live wire and the left hole to the neutr . . .
Comparision Mass Weight Definition Mass is the quantity of matter in a body regardless of its volume or of any forces acting on it. Weight is a measurement of the gravitational force acting on an object. Effect of gravity Mass i . . .
Planet Satellite It is a heavenly body which revolves around the sun and rotates on its axis. It is a heavenly body which revolves around its planet and rotates on its own axis. It has a bigger size It has a smaller size There are . . .
Universe It includes living things, planets, stars, galaxies, dust clouds, light, and even time. Before the birth of the Universe, time, space and matter did not exist. The Universe contains billions of galaxies, each containing millions or billions of stars. The space between the stars and galaxies is largely empty. Astronomy Astrono . . .
Galaxy Constellation It is a collection of billions of stars. It does not form any fixed pattern of any animal or an object. There are around 1011 galaxies in the universe. It is a group of only few stars. It forms the shape of an animal or an object. . . .
Stars are cosmic energy engines that produce heat, light, ultraviolet rays, x-rays, and other forms of radiation. They are composed largely of gas and plasma, a superheated state of matter composed of subatomic particles. Though the most familiar star, our own sun, stands alone, about three of every four stars exist as part of a binary system conta . . .
Some stars have always stood out from the rest. Their brightness is a factor of how much energy they put out–known as luminosity–and how far away from Earth they are. Stars in the heavens may also appear to be different colors because their temperatures are not all the same. Hot stars are white or blue, whereas cooler stars appear to ha . . .
Young stars at this stage are called protostars. As they develop, they accumulate mass from the clouds around them and grow into what are known as main sequence stars. Main sequence stars like our own sun exist in a state of nuclear fusion during which they will emit energy for billions of years by converting hydrogen to helium. Stars evolve over b . . .