Question

Kilowatt-hour is the unit of:
A. Potential difference
B. Electric power
C. Electrical energy
D. Charge

Answer 1

Hint: This is a common unit and we can see this in our electricity bills. By using this we can measure the electric energy consumption in our house. It is the measure of energy consumed in one hour.

Complete Step-by-Step solution:
Kilowatt-hour is a unit of electrical energy. Normally we will use joule as the unit for energy. As we know the power is the rate of energy per unit time.
One watt can be written as the power of one Joule per one second. That’s why we are using watt (W) as the unit of power.
The watt-second is a unit of energy equivalent to one watt of power expended for one second of time. One kilowatt or 1000 watts used for one hour is known as one kilowatt-hour (kwh). It is the same as the actual distance covered by an object within a particular time.
\[1\text{ kilowatt-hour = 1000 watt-hour}\]
\[\begin{align}
  & 1\text{ kilowatt-hour = 1000 watts}\times \text{3600seconds} \\
 & \text{= 3}\text{.6 MJ} \\
\end{align}\]
The kWh is not a standard unit. However, it is commonly used to measure the expenditure of electrical energy by electrical appliances. So, the correct option is C.

Additional information:
For domestic applications kWh is used for the unit of electric energy. But for commercial and industrial applications it may be represented as, Kilo Volt Ampere Hour (kVAh). This value is always higher than the kWh due to the power factor. The ratio of actual power to the apparent power is known as power factor. The kWh is known as the actual power while, kVAh is known as the apparent power. Since the inductive loads normally consume a lot of power without doing any work. It will help you to understand the total energy consumption for a certain period.

Note: Watts is actually telling about the speed of consumption of electricity, therefore it is a unit of power. While kilowatt-hour tells about the amount of electricity used, hence it is a unit of electric energy. All other given options have their own specific units.
\[\begin{align}
  & \text{Potential difference}\Rightarrow \text{Volt} \\
 & \text{Electrical power}\Rightarrow \text{Watt} \\
 & \text{Charge}\Rightarrow \text{Coulomb} \\
\end{align}\]