Question

An electric iron rated 750 W is operated for 2 hours/day. If the cost of the unit is ₹ $3.00$ per kWh, find the cost of energy used to operate electric iron for 30 days.

Answer 1

The electric energy consumed by an appliance is equal to the product of the power consumed by the electric iron and time duration for which the electric iron remains on. 1 unit of energy is equivalent to 1 kW energy consumed in an hour time.

Complete step by step answer:
We’ve been given that an electric iron consuming an electric iron rated 750 W is operated for 2 hours/day. Since the power used by any appliance is equal to the ratio of the energy used to the time for which the appliance stays on, we can say
${\text{Power = }}\dfrac{{{\text{Energy used}}}}{{{\text{time}}}}$
Since, we been given the power used and time duration, we can calculate the energy utilized by the electric iron as
${\text{Energy used = Power}} \times {\text{Time}}$
Since the electric iron consumes 750 W is operated for 2 hours/day, we can calculate the energy used by the electric iron in one day as
${\text{Energy used = 750}} \times {\text{2}}$
$\Rightarrow {\text{Energy used = 1500}}\,{\text{Wh = 1}}{\text{.5}}\,{\text{kWh}}$
The energy used by this electric iron in 30 days will be
${\text{Energy}}\,{\text{Used = 1}}{\text{.5}} \times {\text{30}}$
$\Rightarrow {\text{Energy}}\,{\text{Used = 45}}\,{\text{kWh}}$
Since 1 unit of energy is equivalent to $1\,{\text{kWh}}$ , and one unit of energy costs ₹ $3.00$ , the cost of $45$ units will be:
${\text{Cost = 45}} \times 3{\text{ = 135}}$
Hence it will cost ₹135 to run the iron for two hours daily for one month.

Note:
We must note that an actual electric iron might use different amounts of energy depending on the kind of mode of the electric iron as well as depending on the amount of time it is used in a real-life scenario. We must also remember that 1 unit of energy is equivalent to using 1 kW of power in 1 hour and we can use this relation to determine the number of units required to power an appliance. ‘Units’ is the unit used by power companies to measure the consumption of electricity.