Power | Electrical Power

Rate of doing work is called power. It can also be defined as the rate at which the energy is changed from one form to other.

It is mathematically given by \[p=\frac{dw}{dt}\]

Units of measurement:

Unit of power is the ‘watt’ indicated by
letter ‘W’.

One watt is equal to one joule per second (J/s).

Electrical Power:

In electricity power measured in watts and it is the product of voltage of current.
Instantaneous power p is given by p=vi.
Where v,i are the instantaneous values of voltage and current respectively.

DC power

In DC the instantaneous values can be replaced with their magnitudes as the magnitude is constant.

AC power

In AC voltage and current are function of time. So in AC, average and RMS (root mean square) value were used to measure power.
For sinusoidal wave form the average power or the real power is given as Pavg=VrmsIrmscosθ W
Where cosθ is the power factor and θ is the phase angle between voltage and current.