Question

what is the si unit of electric energy and electric power

Answer 1

he unit of energy is the joule, the unit of power is the watt, and the unit of time is the second. If we know the power in watts of an appliance and how many seconds it is used we can calculate the number of joules of electrical energy which have been converted to sortie other form.


















Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. Electric power is usually produced by electric generators, but can also be supplied by sources such as electric batteries.

Answer 2

Electric power, P : The electric work done per unit time is called electric power. 

Electric power = Electric work done / Time taken 

or   P = W/t 

Electric power is also defined as the electric energy consumed per unit time. P = E/t 

S.I.unit of electric power is Watt. When one joule of energy is used for one second, electric power is equal to one watt. 

Derivation of formula for electric power: 

We know that electric work done, 

W = V x I x t 

P = VIt/t 

P = VI 

Electric power in watts  = Volts x ampere 

Also V = IR .......(According to Ohm's Law) 

So,  P = IR x I 

P = I^2R 

We know that 

I = V/R 

P = [V/R]^2 x R = V^2/R Watt