Hydropower - UNSOLVED PRACTICE SET
Chapter: Sources of Energy | Topic: Hydropower
HYDROPOWER - UNSOLVED PRACTICE SET
Topic: Hydropower
Multiple Choice Questions
Q1. Hydropower (hydroelectric energy) is generated by:
- Burning water to produce steam
- Using the kinetic energy of falling/flowing water to rotate a turbine connected to a generator
- Heating water using solar panels
- Chemical reactions in river water
Q2. In a hydroelectric power plant, water stored in a dam at a height possesses:
- Kinetic energy only
- Gravitational potential energy, which converts to kinetic energy as it falls
- Chemical energy
- Nuclear energy
Q3. Hydropower is generally classified as a:
- Non-renewable source of energy
- Renewable source of energy
- Fossil fuel
- Nuclear energy source
Q4. A major environmental/social concern associated with building large dams is:
- They produce large amounts of CO₂ directly during operation
- Submergence of large areas of land, displacement of communities, and disruption of ecosystems
- They cannot generate electricity at night
- They require fossil fuels to operate
Q5. The amount of electrical energy a hydroelectric plant can generate depends on:
- Only the colour of the water
- The height of the water column (head) and the rate of water flow
- The temperature of the river water
- The number of fish in the reservoir
Q6. Which of the following is a famous hydroelectric project in India?
- Tarapur Nuclear Power Station
- Bhakra Nangal Dam
- Jaisalmer Solar Park
- Mundra Thermal Power Plant
Short Answer Questions
Q7. Explain, step by step, the energy transformations that occur in a hydroelectric power plant, from water stored behind a dam to electricity reaching a consumer.
Q8. Why is hydropower considered a renewable source of energy, unlike coal or petroleum?
Q9. What is meant by the 'head' of water in a hydroelectric plant? How does the head affect the amount of energy that can be generated?
Q10. List two advantages and two disadvantages of large hydroelectric dam projects.
Q11. Why must hydroelectric dams be built in specific geographical locations (e.g., hilly or mountainous regions with rivers)? Can a dam be built anywhere?
Q12. Explain the term 'pumped storage' in the context of hydroelectric plants — how can water be 'reused' to generate electricity again?
Long Answer Questions
Q13. Describe the working of a hydroelectric power plant in detail. Your answer must cover:
(a) the role of the dam in creating a height difference (reservoir),
(b) how potential energy of stored water converts to kinetic energy as water falls through pipes (penstocks),
(c) how this kinetic energy turns the blades of a turbine,
(d) how the rotating turbine drives a generator (recalling the generator principle from the Magnetic Effects chapter), and
(e) what happens to the water after it passes through the turbine.
Q14. The Bhakra Nangal Dam on the Sutlej river is one of India's most significant hydroelectric and irrigation projects.
(a) Describe at least three benefits this kind of project provides to the regions it serves (think beyond just electricity — irrigation, flood control, etc.).
(b) Despite these benefits, large dam projects in India have faced criticism and protests (e.g., concerns about displaced villages, submerged forests). Discuss at least two such concerns.
(c) How do planners try to balance the benefits of hydropower against these social and environmental costs?
(d) Is there a 'perfect' solution, or does every large hydroelectric project involve trade-offs? Explain your view with reasoning.
Q15. Compare hydropower with fossil-fuel-based thermal power in terms of:
(a) renewability — is the 'fuel' (water) replenished naturally?
(b) pollution during operation — does generating electricity from a dam release CO₂ or other pollutants directly?
(c) the construction/setup costs and time required (which tends to be higher for large dams).
(d) the long-term operating costs (which tend to be lower for hydro once built).
(e) Considering all these factors, explain why a country might want a 'mix' of both hydropower and thermal power rather than relying on just one.
Numerical / Application-Based Problems
Q16. Water falls from a height of 80 m at a hydroelectric dam. The mass of water flowing per second is 5000 kg.
(a) Calculate the gravitational potential energy of this water (relative to the bottom) using PE = mgh.
(b) If all this PE converts to KE just before reaching the turbine, calculate the KE per second (this represents the power input to the turbine, in Watts).
(c) If the overall efficiency of the plant (turbine + generator) is 85%, calculate the actual electrical power output.
Q17. A small hydroelectric plant uses water falling from a height of 25 m, with a flow rate of 2000 kg of water per second. (Use g = 10 m/s².)
(a) Calculate the power available from the falling water (Power = mgh/t, where m/t is the mass flow rate).
(b) If the plant operates at 80% efficiency, calculate the electrical power output.
(c) Convert this electrical power output to kWh generated in 1 hour.
(d) How many homes (each using an average of 1 kW) could this plant power simultaneously, based on your answer to (b)?
Q18. Two potential dam sites are being compared:
Site A: height of water fall = 100 m, flow rate = 1000 kg/s
Site B: height of water fall = 50 m, flow rate = 2500 kg/s
(Use g = 10 m/s².)
(a) Calculate the power available (mgh/t) at each site.
(b) Which site offers more power potential?
(c) If Site A is in a remote mountainous area (higher construction cost, smaller reservoir) and Site B is on a wider river plain (lower construction cost, larger reservoir, but more land submerged), discuss (in 2-3 sentences) what additional factors beyond raw power output would influence the choice of site.