The amount of electrical energy that can be generated by a hydroelectric power plant depends upon

Question

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Option B: Quantity of water

Explanation & Concepts:
The electrical energy generated in a hydroelectric plant is directly proportional to the potential energy of the stored water, which is a function of the mass (or quantity) of water and the effective head. While head and quantity both contribute, the quantity of water available is the primary fuel source that determines the sustained power output.

Working Principle: Hydroelectric power plants convert the potential energy of water held at a height into kinetic energy as it flows through a penstock. This kinetic energy strikes the turbine blades, causing mechanical rotation, which the generator then converts into electrical energy via electromagnetic induction. The total power generated is determined by $P = \eta ho g Q H$, where the quantity of water $Q$ acts as the mass flow rate.

Key Formulas: $P = \eta ho g Q H$ — Where P is power (Watts), $\eta$ is efficiency, $ho$ is density, $g$ is gravity, $Q$ is discharge ($m^3/s$), and $H$ is head (m).

Key Points: The total energy generated is proportional to the volume of water ($Q 	imes t$) available.; The head ($H$) provides the pressure, while the quantity ($Q$) provides the mass flow.; Density of water ($ho$) is considered constant at $1000 kg/m^3$.

Advantages: Renewable and clean energy source; Quick starting capabilities for peaking load

Disadvantages: High initial capital cost for dam construction; Environmental impact on aquatic ecosystems

Applications: Base load power stations; Peak load management in grid systems

Additional Info: While all options listed contribute to the power equation, 'Quantity of water' is often emphasized in exams as the variable resource determining the 'amount' of total energy production over time (Energy = Power × Time).. Option A (Head) determines the pressure, Option C (Specific weight) is a physical constant of water, and Option D (Efficiency) is a system parameter.

Answer: B is correct — The total energy generated is fundamentally dependent on the quantity of water discharge available over time.

Exam Tip: Always remember the formula $P = \eta ho g Q H$; if the question asks for 'amount of energy' (Joules), consider the time factor $E = P 	imes t$.

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Option A: Head of water

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Option C: Specific weight of water

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Option D: Efficiency of Alternator

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