ELECTRIC POWER

 The rate of doing work is called as power. Also we can define power as rate of consumption of energy.

 Power = energy/time(T) -(1)

So electric power can be defined as rate of consumption of electric energy.

Equations of electric power

From joules law electrical energy produced = I²RT = VIT = V²T/R

From (1) electric power (P)= I²RT/T = I²R

Power (P) = I²R

or

P = VIT/T = VI

Power (P) = VI

or

P= V²T/R/T = V²/R

Power(P) = V²/R

SI unit of power is watt(W). Since watt is very small for practical purposes we use kilowatt as unit of electric power.

Commercial unit of electric energy 

Electrical energy can be expressed as product of power and time

Electrical energy = power  x time

So commercial unit of electrical energy from the above equation can be given as kilowatt hour (kWh)

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