Watt's Law

Watt's Law, sometimes called the Power Law, describes the relationship between power (PP), current (II), and voltage (VV), so that power is defined as:


Given tha values for any two variables, we solve for the third so that voltage, electrical potential energy, is defined as:


And current, which is the flow of electricity, is defined as:


Power and Watts

Power is measured in watts. One watt (WW) is equal to one joule (JJ) per second (ss), or W=JsW = \frac{J}{s}. Another way to put it is, a watt is the amount of electricity required to accelerate 1kg by 1 meter per second squared (a joule) over 1 second. In other words, a watt is "how much work can be done per second".

Video: Power, Work, and Energy

Full course on Khan Academy: Power)


The terms watt and Watt's Law are named after James Watt, best known for his work to improve the steam engine.

Broader Topics Related to Watt's Law (Power Law)

International System of Units (SI)

Formal terms and definitions of the metric system

Current and Amperes

The flow of electricity, measured in amps

Voltage and Volts

Electrical potential energy, measured in volts

Power (Physics)

Energy that results from charged particles


Energy that results from charged particles

Watt's Law (Power Law) Knowledge Graph