Question

The ultimate source of hydroelectric energy is:
A) Potential energy of water
B) Kinetic energy of water
C) Solar energy
D) Chemical energy

Answer 1

Hint: To reach at the answer to the asked question, you need to know how the hydroelectric energy is produced. Water is stored at some elevated height and a turbine is placed under, when the water is let into the turbine, it makes the turbine move which in turn generates power or energy or electricity. Now, think about what is the generic source of all the conversion of energies in the process. The point where there was no conversion into, i.e. where the energy was originally stored in which state.

Complete step by step answer:
As told in the hint section of the solution, to solve this question, we need to have the understanding of working of production of hydroelectric energy. To produce hydroelectric energy, firstly, the water is stored at an elevated height through the construction of dams. At a lower height, a turbine is installed which can produce energy when it is rotated, and to rotate it, the plan is to use water. We can obviously see that since water is at some height above the turbine, it has potential energy. When the gate is opened and the water is let into the turbine, that potential energy gets converted into Kinetic energy, and this kinetic energy then rotates the turbine, which then converts this kinetic energy into electric energy, or any other energy into which we want to convert.
We can see that all the energies in the process are nothing but the conversion of the potential energy of the stored water, hence, we can safely say that the ultimate source of hydroelectric energy is nothing but the potential energy of water.

Hence, option (A) is the correct answer.

Note: A major mistake that many students make is that they believe that since all the mechanical work is done by the kinetic energy of the flowing or falling water, and then by the kinetic energy of the moving turbine, kinetic energy is the ultimate source of hydroelectric energy, which is a completely wrong approach since. The kinetic energy of the flowing or falling water is nothing but a conversion of the potential energy of the stored water.