What is a kilowatt-hour? How many Joules in 1 kWh?
The correct answer and explanation is :
A kilowatt-hour (kWh) is a unit of energy. It represents the amount of energy consumed or produced when power is used at a rate of 1 kilowatt (kW) over the duration of 1 hour.
Conversion:
1 kilowatt-hour = 3,600,000 joules (J)
This is because:
- 1 kilowatt (kW) = 1,000 watts (W)
- 1 hour = 3,600 seconds
- Energy (in joules) = Power (in watts) × Time (in seconds)
- So, 1 kWh = 1,000 W × 3,600 s = 3,600,000 J
Explanation (300 words):
The kilowatt-hour (kWh) is a common unit used to measure electrical energy. When you see your electric bill, the amount of energy your household has used is often measured in kWh. It’s not a measure of power at a specific moment (like watts), but rather how much energy was used over time.
To understand this better, let’s look at the basic relationship between power and energy. Power is the rate at which energy is used or generated. The unit of power is the watt (W), and 1 watt = 1 joule per second (J/s). So if you run a 1,000-watt (1 kW) appliance for one hour (which is 3,600 seconds), it uses:
1,000 watts × 3,600 seconds = 3,600,000 joules
Hence, 1 kilowatt-hour equals 3.6 million joules.
Joules are the standard SI unit of energy and are commonly used in physics and engineering. However, because joules are relatively small in everyday terms, the kilowatt-hour is more practical for household and industrial energy usage.
For example, if a 100-watt light bulb runs for 10 hours, it uses:
100 W × 10 h = 1,000 watt-hours = 1 kWh
In summary, a kilowatt-hour is simply a way to measure how much energy is used over time, and it equals 3,600,000 joules. This conversion is important in science, engineering, and practical energy consumption.