Power is the rate at which energy is transferred. It tells us how quickly energy is transferred, not how much in total. The equation is: power = energy transferred ÷ time taken, or P = E ÷ t. Where the energy transferred is work done, power = work done ÷ time taken. Power is measured in watts (W), with energy in joules (J) and time in seconds (s).
A 100 W lamp transfers 100 J of energy every second. A 60 W lamp transfers 60 J every second, so it transfers energy more slowly. A device with a higher power transfers more energy in the same time, or the same energy in less time.
Consider two students who climb the same flight of stairs. They have the same mass and lift themselves through the same height, so they do the same work. If one student climbs in less time, that student has the greater power, because power is work done divided by time taken.
Example: a motor transfers 600 J of energy in 12 s, so P = 600 ÷ 12 = 50 W. If 2000 J is transferred in 10 s, then P = 2000 ÷ 10 = 200 W.