Question

An electric heater is rated as \[1500\,{\text{W}}\] . How much energy does it use in \[10\] hours?

Answer 1

Hint:First of all, we will convert the given power into kilowatt-hour. Then we will use the formula which gives us the commercial electrical energy. We will substitute the required values and manipulate accordingly to obtain the desired answer.

Formula used:
The formula which gives the electrical energy used by the device is shown below;
\[E = P \times t\] …… (1)
Where,
\[E\] indicates the electrical energy.
\[P\] indicates the rated power of the device.
\[t\] indicates the duration of time for which the device is used.

Complete step by step answer:
In the given question, we are supplied with the given data:
There is an electric heater which is rated with power as \[1500\,{\text{W}}\] .It is used for \[10\] hours.We are required to find the energy used by the bulb, when used for that amount of duration.

To begin with, we know after analysing the question that it is talked about the commercial use of electrical energy. We will have to first convert the power which is in watts into kilowatts. The duration is already in hours, so we don’t need to convert.Let us solve the numerical. We know,
\[1000\,{\text{W}} = 1\,{\text{kW}}\]
So, we can write:
\[1500\,{\text{W}} = 1.5\,{\text{kW}}\]
Now, we use the formula (1) and substitute the required values in it:
$E = P \times t \\
\Rightarrow E = 1.5\,{\text{kW}} \times 10\,{\text{h}} \\
\therefore E = 15\,{\text{kWh}}$
We know,one unit is defined as \[1\,{\text{kWh}}\] .

So, it consumes energy equivalent to \[15\] units.

Note: While solving this problem, we should always remember that it is a commercial level problem. In this type of problem, we should always use the time in hours scale and the power in kilowatt scale. Failure to use these units will give us irrelevant results. We measure commercial units of energy in units where one unit is termed as one kilowatt-hour.