It is not a strange in physics to define what ‘power’ is. The power is defined to as the energy converted or the rate at which the work is performed.

Consider Δ*W *as the work done and Δ*t* as the time at which the work is done, then the average power can be calculated as

**p**_{avg}= Δ*W/* Δ*t*

The average power or p_{avg} can also be called as just ‘power’. So the average power is the average of work done in unit time. The limiting value of average power is called as the instantaneous power. The work done to produce the constant power under a unit time can be calculated by using the equation

**W=PT**

Power has got different units depending on the situation it is being used. The SI unit is watt (W). It can be joules per second also. Other units are the ergs per seconds or the horsepower.

## Equation of Power in Mechanics

In mechanics the work done is defined using the equation

**W=F. Δ***d*

Where F is the force and Δ*d* is the displacement. It is the force acting on a object and the displacement of the object.

## Power in Electronics and Optics

**In electronics:**

It is the instantaneous electrical power of a component and is written as

*P*(*t*)=* I*(*t*).* V*(*t*)

Where *P*(*t*) is denoted as power in watts or in joules per second. *I*(*t*) is denoted as the current in amperes and *V*(*t*) is denoted as the potential difference across the components in volts. In the case of a resistor the power is written to as

**P=V**^{2}/R

Where R="V/I" which is the resistance in ohms.

**In optics:**

In optics the power is defined to as the average rate of energy transport in a electromagnetic radiation and it is measured in watts. The term power is also used to define the ability of a lens to focus on to light and it can also be defined as the focal length of the lens.