Law of Conservation of Energy

Energy can neither be created nor destroyed, it can only be transformed from one form to another. The total energy before and after transformation remains the same.

Total energy = KE + PE

For example: consider a ball falling freely from a height. At height h, it has only PE = mgh.
By the time it is about to hit the ground, it has a velocity and therefore has KE=
mv2. Therefore, energy gets transferred from PE to KE, while the total energy remains the same.

Power (P)
Power is defined as the rate of doing work or rate of transfer of energy.
Power = work/time
P=W/T

•    Unit of power is watt (W).
Watt

Commercial unit of energy

•    Kilowatt hour (kWh) or 1 unit
•    The energy used in households, industries and commercial establishments are usually expressed in kilowatt hour.
•    1 kWh is the energy used in one hour (1 h) at the rate of 1000 J/s or (1 kW).
∴1 kWh =l kW x U = 1000 W x 3600 s = 3600000 J
1 kWh = 3.6 x 106 J = 1 unit

Power can also be represented as,
P = Fv
F = force applied
v = velocity of object
P=W/t=Fs/t=Fv