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Question: \(1Wh\) (Watt hour) is equal to: a. \(36 \times {10^5}J\) b. \(36 \times {10^4}J\) c. \(3600J\...

1Wh1Wh (Watt hour) is equal to:
a. 36×105J36 \times {10^5}J
b. 36×104J36 \times {10^4}J
c. 3600J3600J
d. 3600Js−13600J{s^{ - 1}}

Explanation

Solution

Hint: Watt-hour is the unit of electrical energy. Remember, 1Watt=1Js−11Watt = 1J{s^{ - 1}} and 1hour=60×60s⁡=3600s1hour = 60 \times 60\operatorname{s} = 3600s

Step by Step Solution:
This problem requires unit conversions to approach the solution.
Firstly, we will need to find which quantity is being represented in the given problem.

Watt hour is a unit of energy that is equal to one watt of power consumed for one hour. Mostly, it represents electrical energy. This unit is used widely in electrical appliances.
Therefore, the quantity being represented in the problem is energy.

The SI unit of energy is Joules(J)(J).
One joule is the energy transferred to a body when a force of 11 Newton is exerted to move a body by a distance of 11 metre.
1J=1Newton−metre1J = 1 Newton - metre
Energy is also equal to the product of the power consumed and the total time taken.
1J=1Watt−second1J = 1Watt - second
We also know that,
1Watt=1Js−11Watt = 1J{s^{ - 1}} and 1hour=60×60s⁡=3600s1hour = 60 \times 60\operatorname{s} = 3600s

Now to approach our solution,
1Watt−hour1Watt - hour should be converted into JoulesJoules.
The units will be considered into observation and will be converted into the SI forms to finally get converted into JoulesJoules.
1Watt−hour=1×3600Watt−seconds=1×3600J1Watt - hour = 1 \times 3600Watt - seconds = 1 \times 3600J
1Watt−hour=3600J1Watt - hour = 3600J

∴\therefore Option (C) is correct.

Additional Data:
The Other units of energy are Electron-volts (eV)(eV), kilo-watt hours(kWh)(kWh), therms, Calories etc.

Note: The students may commit mistakes if they don’t have a proper knowledge of the unit systems and the quantities that are represented by these units.
The quantities like Energy, power, force and time hold a special role in this problem. Their units can be derived by knowing their brief definitions and further can be interrelated to reach conclusions.
But, the main point to remember is that in what context these units are being used. For example, Watt−hourWatt - hour and Electron−VoltsElectron - Volts are used to represent electrical energy and CalorieCalorie is used to represent heat energy.