Question

C(k). Define electric power. Write SI unit of power and derive the formula for electric power.

Answer 1

Concept used: Electric Work

Step 1: Definition of electric power

The work done by the electric current flowing through a conductor (electric work) per unit time is known as electric power.

Mathematically:

$$\begin{gathered} ElectricPower=\frac{Electricwork}{time} \\ P=\frac{W}{t} \end{gathered}$$

Step 2: SI unit of electric power

The SI unit of power is watt and is denoted by W.

Step 3: Derivation of the formula of electric power

When current I flows through a conductor across a potential difference of V for time t, then the electric work done is:

$W=VIt$

So, the electric power can be written as:

$$\begin{gathered} P=\frac{W}{t} \\ =\frac{VIt}{t} \\ =VI \end{gathered}$$

This is the formula of electric power in terms of potential difference across the conductor (V) and the current (I) flowing through the conductor.