Mention the advantages and disadvantages associated with solar cells.

Advantages of solar cells: 1) Solar cells can be set up in remote, inaccessible and sparsely inhabited areas where the laying of usual power transmission lines is difficult and expensive 2) The solar cells are easy to be installed 3) The solar cells produce no noise or pollution 4) The solar cells have a low cost of maintenance Disadvantages of solar cells: 1) The solar cells can convert only 25 % of light energy into electricity and so have low efficiency 2) Silver wire used to connect solar cells for making a solar panel is expensive 3) The special grade silicon needed for making solar cells is costly and its availability is limited 4) The process of manufacturing solar cells is very expensive.

Explain why we are looking at the alternative sources of energy.

We are looking for alternative sources of energy because conventional sources of energy like fossil fuels are non-renewable sources of energy. They are not available in large quantities and cannot be easily replaced. The unlimited use of conventional sources of energy may lead to an energy crisis. The uncontrolled use of fossil fuels created environmental pollution. Another major disadvantage of fossil fuels is that they produce less heat energy. In addition to this, conventional sources of energy are not capable of running the machines to do more and more tasks. Hence, we have to find alternative sources of energy.

Mention two hazards of nuclear power reactor.

In a nuclear power reactor, the process of nuclear fission is carried out for the generation of electricity. The following are the hazards of a nuclear power reactor. 1) There is high cost of installation of nuclear power reactors. The limited availability of uranium fuel is also a major disadvantage. 2) It is difficult to dispose the nuclear wastes as it emits harmful nuclear radiations. 3) There is a risk of leakage of radioactive materials causing serious damage to living things and environment.

Explain how is nuclear energy generated in power reactors. How is electricity produced from nuclear energy?

In nuclear power reactors, the process of nuclear fission is carried out to produce nuclear energy. In this process, the nucleus of a heavy atom (such as uranium, plutonium or thorium) is bombarded with low-energy neutrons. When this is done, the heavy atom will split apart into lighter nuclei. During this process, a tremendous amount of energy is released at a controlled rate. In nuclear power plants, nuclear fission reaction is controlled with the help of control rods made of boron. The released energy is used to generate steam. The steam is utilised by a turbine generator to produce electricity. Since nuclear power plants do not burn fuel, they do not release greenhouse gases.

Write any two hazards of nuclear power generation.

The energy obtained from the nuclear reaction is called nuclear or atomic energy. The source of nuclear energy is the mass of the nucleus. The nuclear energy is released mostly in the form of heat. In nuclear power plants, the process of nuclear fission is used in order to generate electricity. The following are the major hazards of nuclear power generation: 1) There is a risk of leakage of radioactive materials causing serious damage to living things and environment 2) It is difficult to dispose the nuclear wastes as it emits harmful nuclear radiations 3) There is high cost of installation of nuclear power plants

Write the advantages of solar cells.

A device that converts solar energy directly into electricity is called a solar cell. The following are the advantages of solar cells: 1) The solar cells are easy to be installed 2) The major advantage of solar cells is that they can be set up in remote, inaccessible and sparsely inhabited areas where the laying of usual power transmission lines is difficult and expensive 3) The solar cells have a long life and have low cost of maintenance 4) The solar cells produce no noise or pollution

Name the two devices that work using heat energy of the sun.

The sun is one of the major sources of renewable energy. Solar energy consists of heat and light. The device which gets heated by using the sun’s heat energy is called a solar heating device. The solar heating devices are designed in such a way that they help in controlling as much sun’s heat rays as possible. Solar heaters and solar cookers are two devices that work using the heat energy of the sun. The solar cooker is a device that is used to cook food by using heat energy radiated from the sun. A solar heater is a device that uses solar heat energy to produce hot water.

Name the major constituent of biogas. Write the properties of biogas which make it a good fuel.

Biogas is a mixture of gases produced by anaerobic degradation of biomass in presence of water but in absence of oxygen. The gases included in biogas are methane, carbon dioxide, hydrogen and hydrogen sulphide. The major constituent of biogas is methane which is about 75 % . Biogas is a good domestic fuel due to the following reasons: 1) It can be easily transported through pipelines 2) It has a high calorific value 3) It burns without smoke 4) It burns completely without leaving behind any residue