# What is Watt-Hour?

By Xah Lee. Date:

My physics is weak. Was reading up on what exactly a watt-hour is… Here's the summary from Wikipedia.

In physics and other sciences, [ Energy ] [ https://en.wikipedia.org/wiki/Energy ] is a scalar physical quantity that is a property of objects and systems which is conserved by nature. Several different forms, such as kinetic, potential, thermal, electromagnetic, chemical, nuclear, and mass have been defined to explain all known natural phenomena.

In physics, [ force ] [ https://en.wikipedia.org/wiki/Force ] is that which tends to cause a body to accelerate. It may be experienced as a lift, a push, or a pull.

In physics, [ mechanical work ] [ https://en.wikipedia.org/wiki/Mechanical_work ] is the amount of energy transferred by a force.

In physics, [ power ] [ https://en.wikipedia.org/wiki/Power_(physics) ] is the rate at which work is performed or energy is transmitted, or the amount of energy required or expended for a given unit of time.

Now, about the units. The [ newton ] [ https://en.wikipedia.org/wiki/Newton ] is the amount of force required to accelerate a body with a mass of one kilogram at a rate of one meter per second squared.

1 N is the force of Earth's gravity on a apple with a mass of about 102 g.

The force of Earth's gravity on a human being with a mass of 70 kg is approximately 686 N.

The scalar product of force and distance (N×m)— a force of 1 N carried out over a distance of 1 m— is one joule, the basic unit of energy in the SI.

One [ joule ] [ https://en.wikipedia.org/wiki/Joule ] is the work done, or energy expended, by a force of one newton moving an object one meter along.

The [ watt ] [ https://en.wikipedia.org/wiki/Watt ] is a unit of power, equal to one joule of energy per second. A human climbing a flight of stairs is doing work at the rate of about 200 watts. An automobile engine produces mechanical energy at a rate of 25,000 watts while cruising. A typical household incandescent light bulb uses electrical energy at a rate of 40 to 100 watts.

The [ Watt-hour ] [ https://en.wikipedia.org/wiki/Watt-hour ] is a unit of energy. One watt-hour is the amount of (usually electrical) energy expended by a one-watt load (e.g., light bulb) drawing power for one hour. 1 watt-hour = 3600 joules.

In a rough summary, things have energy. Energy exerted is a force. (Force is measured in newton) The ratio of force over time is work. (work is measured in joule) The ratio of work over time is power. (Power is measured in watt)

What exactly is energy is complicated, but i think it ultimately traces to mass by E=mc^2. Effectively, joule is a unit for energy.

Watt-hour is just measure of energy, just like joules. It is a unit used by US American for layperson because they wouldn't understand WTF is a joule.