Question

If an electric iron of 1200 W is used for 30 minutes every day, find electric energy consumed in the month of April.
(a) 12kWh
(b) 18kWh
(c) 36kWh
(d) 6kWh

Answer 1

Hint: As the electrical iron will use the electrical energy in a certain amount of time, we will apply here the formula of energy power to get the right amount of electricity consumed by the iron in a month. The involvement of the month April is to get the specified time of days.

Formula used:
1 kW = 1000 W, 1 hour = 60 minutes, $Energy=Power\times time$

Complete answer:
Electrical energy: Electrical energy is the form of electricity which is produced by the free movements of electrons. When these electrons flow then we say that there is a flow of current inside a circuit.
Electrical iron is a day today gadget by which we iron our clothes.

According to the information given to us we have that the electrical iron is of 1200 Watt which is considered as power. As 1 kW = 1000 W. Time = 30 minutes, and this is used every day for 30 minutes do the usage $30\min \times 30days$. Since, 1 hour = 60 minutes so,
$\begin{align}
  & \Rightarrow Time=30\min \times 30days \\
 & \Rightarrow Time=30\min \times \dfrac{1hour}{60\min }\times 30days \\
 & \Rightarrow Time=\dfrac{1}{2}hours\times 30days \\
 & \Rightarrow Time=15hours \\
\end{align}$
As we know that energy is the product of power and time so, we get
$\begin{align}
  & Energy=Power\times time \\
 & \Rightarrow Energy=1.2kWh\times 15hours \\
 & \Rightarrow Energy=\dfrac{12}{10}kWh\times 15hours \\
 & \Rightarrow Energy=6kWh\times 3hours \\
 & \Rightarrow Energy=18kWh \\
\end{align}$

So, the correct answer is “Option B”.

Note:
To solve any numerical question like this we need to know about the formula and the S.I. unit. In this question we are given the time as 30 minutes only, but this is not the total time used here. The total time will be when the time of 30 minute gets multiplied by the total days of April which is 30. Otherwise, the answer will get wrong. For the right units we have to use 1 kW = 1000 W, 1 hour = 60 minutes conversions. If we do not follow this step then we will get the wrong numerical value of the question.