What Is Watt? - Definition From - TechTarget

What is a watt?

A watt (symbolized W) is the standard unit of power or radiant flux in the International System of Units (SI). It is derived from the SI base units kilogram (kg), meter (m) and second (s), all of which are constructed from the standard's defining constants. The watt is a measure of the rate of energy transfer over a unit of time, with one watt equal to one joule (J) per second:

W = J/s

A joule is the standard unit of energy or work in the SI standard, which defines the joule in terms of kilograms, meters and seconds:

J = kg∙m2∙s-2

A watt can also be expressed in these terms by combining the two previous formulas:

W = J/s = (kg∙m2∙s-2)/s = kg∙m2∙s-3

When applied to electromagnetic energy, the watt refers to the rate at which energy is radiated, absorbed or dissipated.

Understanding power and resource usage is the first step in learning what potential changes can make a difference for data centers, which are heavy users of electric power.

In an electrical circuit -- whether direct current (DC) or alternating current (AC) -- power is the product of the current and voltage. Current, which is measured in amperes (A), is the rate at which the energy flows. Voltage, which is measured in volts (V), is the difference in charge between two points. According to the SI standard, one volt is equal to one watt divided by one amp:

V = W/A

From this formula, we can come up with a formula for calculating watts by multiplying both sides by amps. This gives us the following formula, which indicates that one watt is equal to one volt times one amp:

W = VA

The watt is named after James Watt (1736-1819), a Scottish inventor and engineer. Although he patented several inventions, he is best known for his improvements to steam engine technology, which many consider instrumental in bringing about the Industrial Revolution.