Question

An electric heater of resistance 8 Ω draws a current of 15 A from the service mains operated for 2 hours. What is the cost of the energy to operate it for 30 days at Rs 3.00 per kWh?

• A. Rs. $108$
• B. Rs. $324$
• C. Rs. $360$
• D. Rs. $420$

Answer 1

The correct option is B Rs. $324$

Given: An electric heater of resistance $R=8\Omega$, current drawn $i=15A$, time duration $=2hours$ per day.
Cost of operating $Rs.3perkWh$
The energy $E$ consumed by the heater in 1 day would be
$E=i^{2}Rt={15}^2\times 8\times 2$
Or $E=3600Watthour=3.6kWh.$
The total energy $H$ consumed by the heater in 30 days would be
$H=3.6\times 30kWh=108kWh$
Cost of operating at the rate of $Rs.3/kWh=3\times 108$
$=Rs.324$