Chapter 1, Problem 1.22P

Interpretation Introduction

Interpretation:

The turbines in a hydroelectric plant are fed by water falling from a 50m height. Assuming 91% efficiency for conversion of potential to electrical energy, and 8% loss of the resulting power in transmission, the mass flow rate of water required to power a 200 W light bulb needs to be calculated.

Concept Introduction:

Power can be calculated using energy as follows:

  $\text{Power = energy/time}$

Here, energy can be taken as potential energy which is as follows:

  ${\text{E}}_P\text{ =mgh/time}$

Thus,

  $\text{P = mgh}$

Here, m is mass, g is acceleration due to gravity and h is height.