Define watt-hour. How many joules are equal to 1 watt-hour?

Hint: Watt-hour is an alternate unit of energy used to measure the electrical energy. It is not a standard unit in any formal system, but the watt-hour is commonly used in electrical applications. In general, we know that the energy can be written as the power multiplied by the time.

Complete answer:
Watt-hour is rarely used to measure the energy in any other form of energy other than the electrical energy.

Definition- Watt-hour is an alternate unit of energy used to measure the electrical energy equivalent to a power consumption of one watt for one hour.

As we know that the power is equal to the energy consumed in per unit time, so the energy will be the product of the power and the time.
So here watt is taken as a unit for the power and hour is taken as the unit of the time to calculate the equivalent watt power that has been consumed in one hour.
To calculate the amount of the joules in the watt-hour when we have given with the value of the watt-hour then we multiply the given value of the watt-hour by \[3.6 \times {10^3}\]J.
Hence 1 watt-hour of energy will be having the \[3.6 \times {10^3}\] or $3600$ joules.
So, 1 watt-hour=\[3.6 \times {10^3}\]joules.

Note:
Some confusion may be there that is there any relation between watt and watt-hour? So, we should have a clear idea about the concept of the watt and watt-hour. So, they both are the two different things. The rate at which the energy is produced is called watt whereas watt-hour is the amount of work generated. Watt is a unit of power whereas watt-hour is the unit of energy.