Power in Physics Is Not the Same as Energy
Power is the ability to act or control. In physics it has a precise meaning that everyday speech often blurs.
Power is the ability to act, to control others, or to do work. Physics uses the word far more narrowly than daily speech: power is the RATE at which energy is transferred, measured in watts. Energy is the total amount; power is how fast it flows. A kilowatt-hour on an electricity bill is therefore a unit of energy, not power, even though everyone calls it a power bill. The word comes through Old French from Latin *posse*, to be able, the same root as *possible* and *posse*.
- The ability to act. *The power to decide.*
- Control over others. *Political power.*
- Electrical supply. *The power went out.*
- Rate of energy transfer. *Measured in watts.*
- Latin — *posse*, to be able. *The source.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | power | Real power. |
| Verb | power | Power it. |
| Adjective | powerful | Powerful. |
| Adjective | powerless | Powerless. |
| Unit | watt | 60 watts. |
- She holds real power in the department.Control.
- The storm cut the power.Electricity.
- Power is energy per second.Physics.
Power and energy compared
- Energy — the total amount available, measured in joules
- Power — how fast energy moves, measured in watts
- One watt — one joule per second
- A kilowatt-hour — a unit of energy, not power
- Horsepower — an old power unit, about 746 watts
Old French *poeir*, from Vulgar Latin *potere*, from Latin *posse*, to be able.
What is the difference between power and energy?
Energy is the total amount; power is the rate at which it is transferred. One watt is one joule per second.
Is a kilowatt-hour a unit of power?
No, it is a unit of energy: a kilowatt of power sustained for one hour.