Power is the rate at which work is done or energy is converted. In physics, power is the amount of work done per unit time. It is usually measured in watts (W), but can also be expressed in joules per second (J/s) or calories per second (cal/s). Power has SI units of watts (W). One watt is equal to one joule of work per second, or one calorie of heat per second.
In physics, power is a measure of how much work you can do in a given amount of time. The more power you have, the more work you can do in a given period of time – whether that’s lifting weights, running a marathon, or even just walking up stairs. Power is also a measure of how fast you can do work. So if two people are both lifting the same weight – say, 50 kg – but one person does it in 5 seconds and the other takes 10 seconds, then the first person has twice the power output of the second person.
There are two main types of power: mechanical power and electrical power. Mechanical power is generated by machines like engines and motors. Electrical power comes from batteries and generators. Most homes and businesses use both types ofpower: for example, your home’s furnace may run on electricity while your car engine uses gasoline to create mechanicalpower .
The standard unit for measuring power is the watt (W). One watt equals one joule (J)of energy expended per second – so if something uses 1 Wof power, that means it’s using 1 Jof energy every second. For example, an incandescent light bulb uses about 60 Wof electricalpower , which means it’s using 60 Jof electricalenergy every second it’s turned on. That doesn’t sound like much energy – but over the course of an hour, that adds up to 3 600 J! And if you left that lightbulb on for a full day, it would use 86 400 Jof energy – which equals about 0.24 kilowatt-hours (kWh), or about $0.03 worth of electricity at today’s prices . So even though light bulbs don’t seem like they use much energy when we’re using them moment-by-moment , they actually add up over time!