#### What is power? How do you differentiate kilowatt from kilowatt hour? The Jog Falls in Karnataka state are nearly 20 m high. 2000 tons of water falls from it in a minute. Calculate the equivalent power if all this energy can be utilized? $(g = 10 m s^{-2})$

Solution

Power of anything is defined as the rate of work done by that thing or energy supplied per unit time.
Mathematically, power is defined as the product of force and velocity.
Power = F v.
Power is defined as work done per unit time and its unit will be watt or kilowatt.
If we multiply power with time, we will get energy or work done.
Therefore, kilowatt -hour will be the unit of energy.
[Only kilowatt is the unit of power and that is not unit of energy.]
In one minute all the potential energy of water can be utilised.
Energy utilised = Potential energy = mgh
$PE=(2000\times 10^{3}kg)\times 10ms^{-2}\times 20m$
$=4\times 10 ^{8}Joule$
Now time t = 1 minute = 60 seconds
Hence power will be
$power=\frac{energy}{time}=\frac{4\times 10^{8}Joule}{60seconds}=6.67\times 10^{6}watt$