Coal
The steam engine, which ran on coal or wood, was the first effective use of energy. However, it produced a lot of smoke and pollution, and required constant manpower to feed the engine with fuel. This led to the need for more efficient types of fuel.
Even today, coal is used in several industrial applications. Thermal energy is also made from it. It is found deep below the surface of the earth from where it is mined. The quantity of coal is limited on the earth, so there is need to conserve it. Also, it causes a lot of environmental pollution in the form of smoke and dust.
Mineral oil and Natural gas
Petroleum was first discovered in America in 1857. Gottlieb Daimler saw it burn brightly, and he thought that it could be used as a fuel. He invented an engine in 1885 which ran on petrol. Today, petrol is widely used in a variety of vehicles.
Mineral oil is extracted from deep below the earth’s surface and refined to produce different fuels. Petrol is a refined form of mineral oil, while diesel is a residue of mineral oil. Rudolf Diesel invented the diesel engine specifically to use this residue, which is cheaper than petrol. Diesel is commonly used in large vehicles and machines, such as railway engines, ships, trucks, buses, generators, and some cars. However, both petrol and diesel cause environmental pollution.
In addition to oil, natural gas is also found below the earth’s surface and is extracted using large machines. It is now used as a source of energy for transportation, cooking, and other purposes.
Electricity
Once about 300 years ago, a toy popular among children in the Netherlands was Leyden Jar. It was linked with two wires, one inside the glass and the other outside it.
When the two wires were joined, mild sparks and shocks were produced. The children found it like magic.
During his visit to the Netherlands, Benjamin Franklin, an American scientist, happened
to see this toy. He found it curious. He studied it. He felt that the lightning produced during a thunderstorm was similar to the sparks produced in a Leyden Jar. He felt that this could be a source of energy. He decided to undertake a risky experiment.
On a cloudy day in 1752, Benjamin flew a kite and attached it with a strong silk thread. He also attached a piece of wire to the kite and a metal key at the other end of the thread. He noticed that whenever lightning struck, shocks were produced in the key. He himself felt the shocks. This proved his theory that lightning has electricity.
The discovery of electricity led to a series of inventions aimed at producing it. Alessandro Volta developed the first battery in Italy in 1800, which generated a small but steady flow of electricity. Other scientists then developed generators that could produce a large and continuous flow of electricity. This source of energy was then used in various fields of life.
Electricity has become a common commodity now. It has numerous applications in our daily life. Right from trimmers and blowers to fans and computers to refrigerators and elevators, electricity is used widely. Even cars, buses and trains run on electricity today. If there is no electricity for a few hours, people feel restless. Electricity poles in towns and villages are the mark of progress and modern life today. It has become so important in life that people have installed generators and inverters to get a continuous flow of electricity in homes, offices, shops and other places.
Electricity is classified on how it is produced.
Clean Sources of Energy
Electricity is produced from different sources, like coal or water. We can classify sources of energy into two types conventional sources and non-conventional sources.
1. Conventional sources of energy use coal, mineral oil, natural gas and electricity.
This has certain serious limitations :
2. Non-conventional sources of energy are also called alternative sources of energy.
They are clean sources of energy, like water, wind, sunlight etc. These sources have the following characteristics :
Gobar gas (biogas) energy is becoming viable on a limited scale now.