Case Study:

India generates a large portion of its electricity from thermal power plants, especially coal-based plants located in states such as Uttar Pradesh, Jharkhand, and Chhattisgarh. One such plant near Singrauli supplies electricity to several cities and industries.

In a thermal power plant, electricity generation begins with the burning of coal in a boiler, which releases a large amount of heat energy. This heat converts water into high-pressure steam. The steam is directed toward a steam turbine, where it strikes the turbine blades and causes them to rotate rapidly. 

The rotating turbine shaft is connected to an electric generator. As the turbine rotates, the generator also rotates. Inside the generator, magnets move relative to coils of wire, producing electricity through electromagnetic induction. 

The energy transformation in a thermal power plant occurs in stages:
Chemical energy (coal) --> Heat energy --> Mechanical energy (turbine) --> Electrical energy (generator).

After passing through the turbine, the steam is cooled in a condenser, where it converts back into water and is reused in the boiler, forming a continuous cycle. 

The electricity generated is then sent to transformers, where the voltage is increased for efficient long-distance transmission through power lines to homes, schools, and industries. 

A typical large thermal power unit can generate hundreds of megawatts of electricity, enough to supply power to millions of households. However, burning fossil fuels also produces pollutants such as carbon dioxide and sulfur dioxide, which contribute to environmental challenges.

Thus, thermal power plants demonstrate how the principles of energy conversion, turbines, and electromagnetic induction are applied in large-scale electricity generation.

Questions

Section A - MCQs

1. In a thermal power plant, the turbine rotates mainly due to:

A. Flow of electricity
B. High-pressure steam
C. Magnetic field
D. Cooling water

2. Which energy conversion takes place in the generator of a thermal power plant?

A. Heat energy --> Mechanical energy
B. Electrical energy --> Chemical energy
C. Mechanical energy --> Electrical energy
D. Chemical energy --> Heat energy

3. After passing through the turbine, steam is usually sent to:

A. Boiler
B. Condenser
C. Generator
D. Transformer

4. Why is the voltage increased using transformers before electricity is transmitted over long distances?

A. To reduce energy loss during transmission
B. To increase temperature of wires
C. To reduce current to zero
D. To stop magnetic effects

Section B - Short Answer Questions

1. Explain the role of the turbine in a thermal power plant.

2. How does the generator produce electricity using electromagnetic induction?

3. List the sequence of energy transformations in a thermal power plant.

Section C - Long Answer Question

1. A new thermal power plant is planned near a coal mining region in India.

Analyze the process of electricity generation in the plant and answer the following:

• Explain how heat energy from coal is converted into electrical energy.
• Describe the roles of the boiler, turbine, and generator.
• Suggest one environmental challenge associated with thermal power plants and a possible solution.

Answer Key

MCQ Answers

1. B - High-pressure steam
2. C - Mechanical energy --> Electrical energy
3. B - Condenser
4. A - To reduce energy loss during transmission

Short Answer Solutions

1.mThe turbine converts the kinetic energy of high-pressure steam into mechanical rotational energy, which rotates the shaft connected to the generator.

2. When the turbine rotates the generator shaft, magnets move relative to coils of wire. This changing magnetic field induces electric current in the coils according to electromagnetic induction.

3. Energy transformations:
    Chemical energy (coal) --> Heat energy --> Mechanical energy (turbine rotation) --> Electrical energy (generator).

Long Answer Solution

Electricity generation in a thermal power plant involves multiple steps:

1. Boiler: Coal is burned to produce heat, converting water into high-pressure steam.
2. Turbine: The steam rotates the turbine blades, producing mechanical energy.
3. Generator: The rotating turbine spins the generator, where electromagnetic induction produces electrical energy.

Environmental challenge:
Burning coal releases greenhouse gases and air pollutants.

Possible solution:
Installing pollution-control devices such as electrostatic precipitators and scrubbers, and gradually shifting toward cleaner energy sources.