Question

Smallest commercial unit of energy is
A. Kilowatt hour
B. Watt second
C. Watt hour
D. Watt minutes

Answer 1

Hint: We are asked to find the smallest commercial unit of energy. At first understand what is meant by commercial and commercial units. Recall the relation between power and energy. Check how their units are related. Use these facts to select the correct option.

Complete answer:
By commercial we mean dealing with or engaged in marketing or business.
Commercial unit can be defined as the unit of goods used for commercial purposes that is for marketing or business.

Unit of energy is joule. Power is the energy per unit time and unit of power is joule per second which is also known as watt.
\[1\,{\text{watt}} = 1\,{\text{joule}}\,{\text{per}}\,{\text{second}} \\
\Rightarrow {\text{1}}\,{\text{watt}}\,{\text{second}} = 1\,{\text{joule}} \]
One watt second is the energy consumed by an electrical appliance having power one watt in second.

The commercial unit of electrical energy used is kilowatt hour which is energy consumed by an electric appliance of power one kilowatt in one hour.
But the smallest commercial unit of electrical energy used is watt hour which is energy consumed by an electric appliance of power one watt in one hour.

Hence, the correct answer is option C.

Note:Remember there are three fundamental units which are length \[{\text{L}}\], mass \[{\text{M}}\], time \[{\text{T}}\]. There are two types of units; SI unit which is International system of Units and CGS unit which is Centimetre Gram Second unit. SI units of length, mass and time are metre, kilogram and second respectively and CGS units of length, mass and time are centimetre, gram and second respectively.