Question

(a) What is the difference between a thermal power plant and a hydropower plant?
(b) Which of the two causes serious air pollution and how?

Answer 1

Hint:
- One of them converts heat energy into electricity while the other converts potential energy into electricity.
-Thermal power plants are of many types, while hydropower plants are of a single type.
- The thermal power plants are known to combust fossil fuels to produce heat, steam and eventually electricity.

Complete answer:
(a) The main purpose of both Thermal and Hydropower plants is to generate electricity. The raw materials and the processes involved, make them very different from each other.

Thermal power plant	Hydropower plant
In thermal power plants, electricity is produced by burning different types of fuels to generate heat. This heat is then used to boil water.	In hydropower plants, huge dams are built. These dams hold water at great heights. Since the water is at a great height, it has very high potential energy.
The boiling water turns into steam and the pressure of the steam is used to turn turbines. These turning turbines generate electricity.	When this water is released from the dam, it falls down on huge turbines, thus rotating them. This generates electricity.

(b) Out of the two types of plants, it is the thermal power plant that causes serious air pollution. This is because it uses fossil fuels, i.e. coal and its other derivatives. These fuels when burnt, release harmful gases into the environment, such as carbon monoxide and greenhouse gases such as carbon dioxide. Hydropower plants on the other hand do not cause any air pollution at all.

Note: To prevent further air pollution, nowadays nuclear energy is used to generate electricity. In this type of plant, there is no burning of fossil fuels and thus no air pollution. But it has other problems as it uses radioactive elements to generate nuclear energy.