What is the commercial unit of electric charge?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Kilowatt hour
The kilowatt hour (kWh) is the commercial unit of electrical energy: the energy used by a 1 kW appliance running for one hour. It is the “unit” of electricity on which a household bill is charged.
\(1\,\mathrm{kWh}=1000\,\mathrm{W}\times3600\,\mathrm{s}=3.6\times10^{6}\,\mathrm{J}\)
Why the other options are incorrect
Option (1) Volt — Incorrect. The unit of potential difference, the work done in moving a unit charge.
Option (2) Watt — Incorrect. The unit of power, the energy used per second.
Option (3) Ampere — Incorrect. The unit of electric current, the charge flowing per second (1 A = 1 C/s).
Note: It seems that there is a mistake in the original NTA paper, which prints “electric charge” when it should read “electrical energy”. The unit of electric charge is the coulomb, and none of the options is a unit of charge; read as “electrical energy”, the question has the kilowatt hour, Option (4), as its answer.