Question

A house is fitted with ten lamps of each 60 W. Each lamp burns for 5 hrs a day on an average. The cost of consumption in a month of 30 days at 2.80 rupees per unit is:
A) $Rs.152$
B) $Rs.252$
C) $Rs.352$
D) $Rs.452$

Answer 1

In order to calculate the cost of consumption in a month, we need to apply the energy and power formula as mentioned below.
Total energy spent is given by,
$E = nE\prime$, where $n$ is the number of bulbs and $E\prime$ is Energy spent by each bulb.

Complete step by step answer:
$E\prime = Pt$
$E\prime =60\times 5\times 30~Wh$
$E = 60 \times 5 \times 30 \times 10$
$~~=9000\times 10$
$= 90KWh$
$Cost~=90\times 2.8$
$= 28 \times 9$
$= Rs.252$

Hence, the answer to this question is option (b).

Additional Information: The rate at which the electric energy enters the portion of the circuit is called the electrical power input. The rate at which work is done in bringing the charged particles from one point to another is known as electric power. It is denoted by P.Electrical energy use equals the power of the appliance multiplied by the amount of time the appliance is used.The SI unit of power is watt (W). One watt is the power consumed by the device casting 1A of current when operated at a potential difference of 1 V.

Note: While solving this question, we should be aware of the different types of formula used here. The formulae are basically from energy and power and how the different values of the variable of the formula is used from the question. The formula is modified and used here to take out the required solution for the problem given here. Different formulae are used here which must be taken into consideration while solving the question.