Question

Define electric power. An electrical device of resistance R is connected across a source of voltage V and draws a current I. Derive an expression for power in terms of current and resistance.

Answer 1

Electric power is defined as the rate of consumption of energy or simply the rate of doing work.
i.e., power, P =`(" work done"("W"))/("Time"("t"))` ..............(i)

The work done by current (I) when it flows in a potential (V) for time (t) can be given by

W = VIt …………………. (ii)

⇒ Power, P `= "VIt"/"t"="VI"`

∴Electric power, P = VI

From Ohm's law, V=VI

Thus, electric power is given by, P = (IR)I = I²R