Final answer:
Power is the rate of energy usage, measured in watts, and represents how much energy is used or converted over time. Energy consumption is often expressed in kilowatt-hours because it's a larger and more practical unit for household energy use, with 1 kWh equaling 3.6 million joules.
Step-by-step explanation:
The term power is defined as the rate of energy usage. In physics, power is the amount of energy transferred or converted per unit of time. The standard unit of power is the watt (W), which is equivalent to one joule per second (J/s). When considering electrical appliances, power is typically represented as P = W/t = Elt, where P is power, W is the energy consumed, t is the time, and E is the energy supplied by the electricity company. Hence, the energy consumption of an appliance over time t can be calculated as E = Pt.
To understand why energy consumption is sometimes listed in kilowatt-hours (kWh) rather than joules (J), one must look at practicality and scale. Kilowatt-hours are a larger unit of energy, making them more suitable for measuring the large amounts of energy that appliances typically use over time. The relationship between these units is straightforward: 1 kWh equals 3.6×106 joules, allowing for conversion between the two.