Question

One kilowatt hour is equal to:-
A. $36 \times {10^5}$ Joules
B. $36 \times {10^3}$ Joules
C. ${10^3}$ Joules
D. ${10^5}$ Joules

Answer 1

Hint: In order to solve this problem you need to know that one kilowatt hour is thousands joules per second. Knowing this will solve your problem and give you the right answer after doing the conversion of time and multiplying the kilowatt in with hour in terms of seconds.

Complete step-by-step answer:

We know that,
1 kilo watt = 1000 joules per second.
We also know that 1 hour = 3600 seconds.
Therefore, we can say 1 kilowatt hour is $1000\dfrac{J}{s} \times 3600s$= 3600000 Joules = $36 \times {10^5}$ Joules.
Hence, one kilowatt hour is 3600000 joules.

So, the correct option is option A.

Note: It is the problem of conversion of units. Students can easily solve these questions if they have studied units and measurements thoroughly. Knowing units and measurements will help you in various competitive exams. Here we have first converted the kilo into 1000 and then we have converted the unit of power into joules per second. As we have asked to get the answer in joules so we have converted 1 hour into seconds and then multiplied it with joules per second and then the terms of seconds got cancelled and we got the answer in joules. Doing this in most of the problems of units and measurement will solve your problem and will give you the right answer and making strong the concept of units and measurement will help you many times.