Question

The consumption of electrical energy in the house is measured in terms of:
A) Kilowatt hour
B) Watt hour
C) Joules
D) Kilo joules

Answer 1

When electric current is passed through the appliances which are used in our houses, then the electrical energy gets converted to other forms of energy. This is called the consumption of electrical energy.

To measure the electrical energy consumption, we need a unit in which the electrical energy consumption can be represented.

Step-by-step solution:
When electric current passes through an electrical appliance then electrical energy is consumed to do the work. The electrical appliances convert the electrical energy into another form of energy.

Using Joule’s law, when an electrical current$i$is passing through an electrical appliance of resistance$R$then the electrical power consumption is given by
$P={{i}^{2}}R$
Using Ohm’s law, when an electric current$\left( i \right)$ is passing through the resistor of resistance$R$then potential difference across the resistor is given as,
$V=iR$
Then putting the value of$i$in equation of Joule’s law, we get
$P=\dfrac{{{V}^{2}}}{R}$
The SI unit of electric power is watt$\left( W \right)$, where $1W$=1volt\times 1ampere$$$$=1V\times 1A.
1 Kilo watt or 1$kW$ = 1000$W$
As electrical appliances run for a long time. So, a unit must be allotted for the energy consumption which covers the long run of electrical appliances in our households.
Consumption of electric energy is generally measured in Kilowatt and the unit of electric energy is Kilowatt hour$\left( kWh \right)$.
Therefore,
$1kWh=1000watt\times 1hour=1000W\times 3600s$
Or,
$1kWh=3.6\times 106watt/second=3.6\times 106Joules$.
The electrical energy consumed in our houses is measured in a$kWh$.
Hence, the power consumption of electricity is generally measured in kilowatt and the unit of electric energy is kilowatt hour$\left( kWh \right)$.

Therefore, option A is the correct answer.

Note:
-To find the numerical value of a physical quantity from one unit to another, we use unit conversion method.
-When electric power is multiplied with the time interval then we get the electrical energy consumption.
-Students should be careful about the unit conversion of time from hour to second.