| Symbol | W |
|---|---|
| Equivalence | 1 W = 1 J/s |
| Quantity | Power |
Definition and context
The watt expresses the rate of energy transfer and is written with the symbol W. A power of one watt is equivalent to one joule per second. The symbol retains its capital letter and does not change when writing a plural.
Reading watts on a label requires identifying which power is being stated: an electrical input, a useful output, or a value under test conditions. In a made-up example, two devices might consume 40 W and produce different amounts of light. Comparing that output would require another quantity and an appropriate procedure. The watt helps organize the energy balance, but by itself it does not summarize the quality of the service provided by the device.
What we know and its limits
Introductory reference sheet. Properties and applications depend on measurement conditions; consult the sources before making comparisons.
Follow the evidence
The original sources for exploring this explanation and its limits.
- Special Publication 330 · The International System of Units
National Institute of Standards and Technology
Definitions of the SI and relationships between quantities and units.
Image credits
SciClue · AI-generated illustration (OpenAI) · Original source · Recurso editorial de SciClue · generado con IA