Question

define electric power and electrical device of resistance R is connected across a source of voltage v and draw a current I drive an expression for power in term of voltage and resistence​

Answer 1

Definition:

Time rate of change of energy is called as power. It is also defined as product of current and voltage.

Mathematically:

P = W/t

It can also be written as  

P = IV

If voltage across resistor R is constant then using ohm’s law we get,

P = V^2/R

If current through resistor R is constant then using ohm’s law we get,

P = I^2R