Question

A 1kW heater is meant to operate at 200V. How many units of electrical energy will it consume in a month (of 30 days) if it operates 10 hours daily at the specified voltage of 200 V?

Answer 1

Hint
Electrical appliances consume energy to perform work, and this provides a measure for their power. The electrical energy and power depend directly on each other including a factor of time for which the appliance is in operation.
$\Rightarrow E = P \times t$, where E is the total electrical energy consumed, P is the power of the electrical appliance, and t is the time period for which it is in operation.

Complete step by step answer
In this question, we are provided with the following data for a heater:
Power of the heater $P = 1kW = 1000W$[As 1 kW = 1000 W]
Voltage of operation $V = 200$V
Time of operation in days: 30
Time of operation in hours per day: 10
From this, we can calculate the total time of operation as the product of the number of days of operation and the daily hours. We get the total time as:
$\Rightarrow t = 30 \times 10 = 300$hours
We know that the total electrical energy consumed can be calculated as:
$\Rightarrow E = P \times t$
Putting the known values in this equation gives us:
$\Rightarrow E = 1000 \times 300$Wh
$\Rightarrow E = \dfrac{{1000 \times 300}}{{1000}}kWh = 300kWh$
This is the total energy consumed by the heater in a span of 30 days.

Note
The electricity bill on an appliance is calculated by using the total energy consumed by it. As we saw, the total energy depends both on the power of the electrical appliance and the time for which it operates. That is why leaving the lights and fans switched ON when not in use adds so much to the bill even when their power is low. The total energy is also measured in kWh, and not in Wh.