Power
Definition
How fast work gets done — the rate at which energy is transferred or converted.
Symbol: · Unit: watt (W)
Technical definition
The time rate of doing work, P = W/t, equivalently P = Fv for a constant force acting in the direction of velocity. Power is a scalar measured in watts.
Example
A 100 W light bulb converts 100 joules of electrical energy into light and heat every second. A 2000 W hair dryer does the same job twenty times faster — same energy per second, twenty times the rate.
Power is not energy. A 60 W bulb and a 1000 W microwave both use energy, but the microwave transfers it far faster — that is why food heats in minutes, not hours. Saying a battery 'has a lot of power' when you mean it stores a lot of energy mixes up the rate (watts) with the total (joules or kilowatt-hours).