Fossil fuels like coal and petroleum results in air pollution as there is release of huge amount of pollutants.
Gases such as carbon dioxide is released when a fossil fuel is burnt, which causes global warming.
Soil fertility and potable water is affected by the oxides of carbon, nitrogen, sulphur, etc. that are released from fossil fuels.

Question - 5 : - Why are we looking at alternate sources of energy?

Answer - 5 : - The reason why we are looking at alternate sources of energy is because the fossil fuels are non-renewable sources of energy, i.e. they are not available in large quantities and cannot be replenished. Fossil fuels will get exhausted if their consumption is not controlled. Therefore, it is better to switch to alternate source of energy.

Question - 6 : - How has the traditional use of wind and water energy been modified for our convenience?

Answer - 6 : -

In olden days, wind energy was trapped used windmills to do mechanical works like lifting or drawing water from a well. But these days, windmills are used to generate electricity. The kinetic energy of wind is trapped and converted into electricity with the help of rotatory motion of the blades, which turns the turbine of the electric generator to produce electricity.

Similarly, waterfalls were the source of potential energy in olden days. But these days as the number of waterfalls has reduced, water dams are constructed and are used as a source to trap the potential energy. Here, the water falls from a certain height on the turbine producing electricity.

Question - 7 : - What kind of mirror – concave, convex or plain would be best suited for use in a solar cooker? Why?

Answer - 7 : - For a solar cooker the heat source is sunlight for heating and cooking. The reason why a mirror is used is to reflect and focus the sunlight at one point. So a concave mirror can be used in a solar cooker, as it focuses all the sunlight at one point resulting in increase in temperature, thereby heating and cooking the food.

Question - 8 : - What are the limitations of the energy that can be obtained from the ocean?

Answer - 8 : -

The different forms of energy that can be obtained from the ocean are tidal energy, wave energy and ocean thermal energy. Following are the limitations of the energy obtained from ocean:

• The relative positioning of the earth, the sun and the moon has an impact on the tidal energy.

• For the conversion of tidal energy into electricity, high dams are required.

• To obtain electricity from wave energy, very strong waves are required.

• For trapping the ocean thermal energy, there should be a temperature difference of more than 20°C between hot surface water and the cold water at a depth.

Question - 9 : - What is geothermal energy?

Answer - 9 : - Geothermal energy can be defined as the energy that is obtained from the earth. The energy can be obtained from the hot spots that are formed when the molten rocks at the core of the earth are pushed to the earth’s crust. Hot springs are used for the production of electricity in the geothermal power plants.

Question - 10 : - What are the advantages of nuclear energy?

Answer - 10 : -

Following are the advantages of nuclear energy:

• Amount of energy produced per unit mass is large

• As it does not produce any pollutants, it is clean

• Fission of 1 atom of uranium produces 10 million times the energy that is obtained by burning 1 atom of carbon

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