Question

derive the formula and SI unit of electric power

Answer 1

Power is the amount of work done (or energy consumed) per unit time.
Let , Work done = W joules
Time taken = T seconds

$power = \frac{work \: done}{time \: taken}$
$\: \: \: \: \: = \frac{w}{t} joules \: per \: second$
$power = \frac{w}{t \:} \: watt$
Hence, Power = Work done / Time taken
The SI unit of power is joules per second or 'Watt'.

Answer 2

Answer:

Explanation:

When a current I flows through a conductor under a potential difference of V for time t, the electric work done is given by,

Electric work done, W = VIt

Electric Power,         P = VIt/t = VI

So, When a current of I amperes flows through a conductor under a potential difference of V volt, then

Electric power,  P = V volt × I ampere = VI volt-ampere

                          P = VI watt = VI watt

                          P = VI W

Where V is the potential difference across the conductor in volts,

I is the current in the amperes flowing through the conductor.

So, if voltage and current are known, powers of an electrical appliance can be calculated.