Question

Practical unit of power are:
A. kW
B. MW
C. GW
D. hp

Answer 1

Hint: The practical unit of an electrical instrument is the unit used for convenience in measuring the magnitudes in practical applications. Therefore, the practical unit of power must be used to express the power rating for appliances such as electric motors.

Complete step by step answer:
To answer this question, we need to understand what is a practical unit? The practical unit of an electrical instrument is the unit used for convenience in measuring the magnitudes in practical applications. Therefore, this unit should be used in day to day life.
We know that 1 kW is equal to \[{10^3}\,{\text{W}}\]. Attic fans use 1 kW power. This is a relatively bigger unit of power and cannot be used in daily life. Therefore, the option (A) is incorrect.
We know that 1 MW is equal to \[{10^6}\,{\text{W}}\]. Hot tub uses approximately 1 MW power. This unit of power is not used in daily life for rating the appliances. Therefore, the option (B) is incorrect.
We know that 1 GW is equal to \[{10^9}\,{\text{W}}\]. This unit is used in large industries where usage of electricity is at peak. This unit of power is not used in daily life for rating the appliances. Therefore, the option (C) is incorrect.
We know that 1 hp is equal to 746 W. Home appliances and many industrial appliances use this unit of power for rating of electric appliances. The submersible pumps, well pumps and other motors have power ratings given in hp. Generally we use the motors from 1 hp to 10 hp. Therefore, hp is the practical unit of power.

So, the correct answer is “Option D”.

Note:
The unit used to measure the power in an electric resistor cannot be said to be a practical unit as it is very small. To understand what the meaning of a practical unit is, consider the measurement of capacitance. The capacitance of any electrical capacitor is always in microfarads to millifarads. The farad is a much larger unit of capacitance and nothing had that much of capacitance. Therefore, the practical unit of capacitance is microfarad.