A Level Physics Practice Exam

What does a kilowatt hour represent?

1. A measurement of voltage

2. A measurement of power

3. A measurement of energy

4. A measurement of current

The correct answer is: A measurement of energy

A kilowatt hour is fundamentally a measurement of energy. It quantifies the amount of energy consumed or produced over a period of time. Specifically, it represents the energy used by a device with a power rating of one kilowatt (1 kW) operating for one hour. To break it down, power is the rate at which energy is used or produced, and it's measured in watts (where one kilowatt equals 1000 watts). When you multiply power (in kilowatts) by time (in hours), the product gives you energy in kilowatt hours. Therefore, when you see a kilowatt hour in contexts such as electricity billing, it indicates how much energy has been consumed during that time period. The other options involve measurements that are distinct from energy. Voltage measures electric potential difference, power refers specifically to the rate of energy transfer, and current defines the flow of electric charge. Thus, kilowatt hour uniquely signifies energy consumption or production, making it the correct answer.