Question

In what unit does the electric meter in a house measure the electrical energy consumed? What is its value in S.I. unit?

• A. $Wh,1Wh=3.6\times {10}^{6}J$
• B. $kWh,1kWh=3.6\times {10}^{5}J$
• C. $W,1W=3.6\times {10}^{6}J$
• D. $kWh,1kWh=3.6\times {10}^{6}J$

Answer 1

The correct option is D $kWh,1kWh=3.6\times {10}^{6}J$

The electrical energy consumed in our houses are measured in a kWh.
The SI unit of electric power is watt (W), where $1W=1volt\times 1ampere=1V\times 1A$.
1 kilo watt or 1kW = 1000 W.
Consumption of electricity (electric energy) is generally measured in kilo watt and the unit of electric energy is kilo watt hour (kWh).
Therefore,
$1kWh=1000watt\times 1hour=1000W\times 3600s$
Or,
$1kWh=3.6\times {10}^{6}watt/second=3.6\times {10}^{6}Joules$.
Hence, the power consumption of electricity is generally measured in kilo watt and the unit of electric energy is kilo watt hour (kWh) or $3.6\times {10}^{6}J$.