Question

What is the smallest unit of power?

• A. Watt
• B. Kilowatt
• C. Horsepower
• D. Milliwatt

Answer 1

The correct option is D

Milliwatt

The explanation for the correct option:

Definition of power

1. Power is defined as the rate of doing work with respect to time.
2. The mathematical expression of power is : $\mathrm{P}=\frac{\mathrm{W}}{\mathrm{t}}$, where $\mathrm{W}$ is the work done, $\mathrm{t}$ represents time, and, $\mathrm{P}$ represents power.
3. The dimension of power is $[{\mathrm{M}}^1{\mathrm{L}}^2{\mathrm{T}}^{-3}]$.
4. The SI unit of power is Watt.

The explanation for right option :

1. Milliwatt is the smallest unit of power among the given options.
2. It is denoted by $\mathrm{mW}$.
3. $1\mathrm{mW}={10}^{-3}\mathrm{W}$.

The explanation for incorrect options:

1. The power of machines and motor vehicles is expressed in horsepower (hp). $1\mathrm{hp}=745.7\mathrm{watt}$.
2. Kilowatt is the unit of power used to measure electric power and is equal to $1000\mathrm{W}$.
3. Watt is the SI unit of power. It is defined as the energy consumed at the rate of $1$ joule per second.

Hence, option (d) is the correct answer.