Define kilowatt-hour. How many joules are equal to 1 kWh
The Correct Answer and Explanation is:
Definition and Explanation:
A kilowatt-hour (kWh) is a unit of energy commonly used to measure electrical energy consumption. It represents the amount of energy used when a device with a power rating of 1 kilowatt operates continuously for 1 hour.
To understand this better, we break it down:
- “Kilo” means one thousand.
- A watt is a unit of power equal to 1 joule per second.
- Therefore, 1 kilowatt = 1000 watts = 1000 joules per second.
If a 1-kilowatt appliance runs for 1 hour (which is 3600 seconds), the total energy consumed is:Energy=Power×Time=1000 J/s×3600 s=3,600,000 joules\text{Energy} = \text{Power} \times \text{Time} = 1000 \, \text{J/s} \times 3600 \, \text{s} = 3,600,000 \, \text{joules}Energy=Power×Time=1000J/s×3600s=3,600,000joules
So, 1 kilowatt-hour is equal to 3.6 million joules (3,600,000 J).
explanation:
The kilowatt-hour is a unit of energy used mainly for measuring electricity usage. Unlike power, which describes how quickly energy is used or generated, energy itself measures the total amount of work done or heat transferred over time.
The term “kilowatt-hour” combines both a unit of power and a unit of time. When we say an appliance uses 1 kilowatt-hour of energy, we mean that it has used the energy equivalent of operating a 1000-watt (or 1-kilowatt) device for one hour. Since a watt is equal to one joule per second, 1000 watts equal 1000 joules per second. Over the course of one hour, which contains 3600 seconds, the total energy consumed becomes 1000 × 3600 = 3,600,000 joules.
Understanding the relationship between kilowatt-hours and joules helps in comparing different energy units and converting measurements depending on context. Scientists and engineers prefer joules for precision in calculations, especially in physics and chemistry. However, kilowatt-hours are more practical for everyday use, such as reading an electricity bill.
If you see a bill indicating you used 500 kWh in a month, that means you consumed 500 × 3.6 million = 1.8 billion joules of energy. This perspective shows how much energy everyday appliances use, helping users to be more mindful about consumption and efficiency.
