The total power output in a hydroelectric installation depends upon
A. the total water flow
B. the electrical conductivity of water
C. atmospheric temperature
D. vertical distance through which water falls
Choose the correct answer from the options given below:
A and D only
The total power output of a hydroelectric installation follows the standard hydropower relation P = ρgQH, where ρ is the density of water, g is the acceleration due to gravity, Q is the rate (volume per second) of water flowing through the turbine, and H is the head, i.e., the vertical distance through which the water falls before striking the turbine blades.
This equation shows the output depends directly on two physical quantities: (A) the total water flow (a larger discharge means more mass of water striking the turbine every second) and (D) the vertical fall (head), since a greater fall height gives the water greater potential energy, which converts to greater kinetic energy and hence more electricity.
(B) Electrical conductivity of water is irrelevant here — a hydro turbine-generator converts mechanical energy from falling water into electricity through electromagnetic induction; the water itself is not carrying current, so its conductivity does not enter this formula.
(C) Atmospheric temperature similarly plays no role in the mechanical energy conversion process of a hydro plant.
Therefore, only the water flow and the vertical fall (head) govern the total power output, making A and D only the correct combination.
Note: This question was officially dropped by UGC NET (all candidates were awarded marks for it), but going strictly by the hydroelectric power formula P = ρgQH, the physically correct answer is A and D only, as explained above.
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