Question

A household uses the following electric appliances:
A) Refrigerator of rating for each day $400W$
B) Two electric fans of rating $80W$each for $6h$ daily
C) Six electric tubes of rating $18W$each for $6h$ daily
Calculate electricity bill for the household for the month of June if cost of electrical energy is $3$per unit.

Answer 1

Recall that the energy is a property of matter. It is defined as ‘the ability to do work’. The energy can exist in various forms like kinetic energy, potential energy, electrical energy etc. It is transferred from one form to another form. It is the strength required to do any physical activity.

Complete step by step solution:
Formula for energy is
$Energy = Power \times Time$
Energy consumed per day by the refrigerator is $= 400W \times 10h$
Converting watts into kilowatt, the above equation can be written as
$E = \dfrac{{400}}{{1000}}kW \times 10h$
$E = 4kWh$
Similarly energy consumed per day by the fans is$= 2 \times 80W \times 6h$
Converting watts into kilowatts,
$E = 2 \times \dfrac{{80}}{{1000}}kW \times 6h$
$E = 0.96kWh$
Energy consumed per day by the electric tubes$= 6 \times 18W \times 6$
Converting watts into kilowatts
$E = 6 \times \dfrac{{18}}{{1000}}kW \times 6h$
$E = 0.0648kWh$
Total energy consumed per day by all the appliances is the sum of the individual energy consumed. Therefore it can be written that
$\Rightarrow {E_{total}} = 4 + 0.96 + 0.648$
${E_{total}} = 5.608kWh$
The total energy consumed in 30 days$= 30 \times 5.608kWh$
$\Rightarrow 168.24kWh$
Cost of electrical energy is given. So electricity bill of the household $= 168.24 \times 3$
$\Rightarrow$Cost of electricity bill $= 504.72$

Note : It is important to know that as per the law of conservation of energy, the energy of an isolated system remains constant. It is always conserved. This is one of the important properties of energy. Therefore, it can never be created nor destroyed. The process of movement of energy from one place to another is known as energy transfer. It goes on all the time in the universe. The law of conservation of energy is also known as the first law of thermodynamics.