Question

An electric kettle is rated as 2.5kW, 205V. Find the cost of running the kettle for two hours at 60 paise per unit.
A) ${\text{Rs}}.6$
B) ${\text{Rs}}.3$
C) ${\text{Rs}}.9$
D) ${\text{Rs}}.1$

Answer 1

Hint: The cost of the electrical energy depends upon the energy consumed by the appliance and the cost of energy consumed per unit whereas the energy consumed will depend upon the power of the appliance and the time is taken.

Formula used:
The formula of the energy consumed by an appliance for t hours is given by
${\text{E}} = {\text{P}} \times {\text{t}}$ where $E$ is the energy consumed $P$ is the power and $t$ is the time taken.

Complete step by step answer:
As it is given that the power of the electric kettle is $2.5{\text{kW}}$ and the voltage of the kettle is $205{\text{V}}$ and the kettle is switched on for 2 hours.
So the energy consumed by the electric kettle is given by,
$\Rightarrow {\text{E}} = {\text{P}} \times {\text{t}}$
$\Rightarrow {\text{E}} = 2.5 \times 2$
$\Rightarrow {\text{E}} = 5{\text{kWh}}$
As the cost for electricity consumed per ${\text{kWh}}$ is 60 paisa per unit.
The cost of the electric kettle is equal to,
$\Rightarrow {\text{C}} = {\text{E}} \times {\text{rupees per unit}}$
$\Rightarrow {\text{C}} = 5 \times 0.60$
As the cost per unit is 60 paisa per unit.
$\Rightarrow C=300 $ paisa
$\Rightarrow {\text{C}} = {\text{Rs}}.3$

$\therefore$ The cost of running the kettle for two hours is Rs.3. Hence, the correct option is option (B).

Note:
It is advisable for students to remember the formula for calculation of the energy consumed by the electric appliance as it can help in solving these types of problems. The cost of energy consumed per unit is 60 paisa per unit and as 1 rupee has 100 paisa and therefore we multiply 0.60 with the total energy consumed.