Watt's law
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Watt's law is an unofficial name sometimes given to a formula that enables one to calculate the electrical power dissipated in a resistor given the potential difference across it and the current flowing in it.
The law is represented by the formula: [1]
where
- P is the amount of power in watts
- V is the potential difference in volts
- I is the current in amperes
The potential difference is also known as the voltage drop, and is sometimes designated by E or U instead of V.
Watt's law can, when combined with Ohm's law, be rewritten as follows:
where
- R is the electrical resistance in ohms.
[edit] Naming
The name Watt's Law is used only informally, and is not found in authoritative sources such as technical dictionaries [2][3]. This is because the law is a combination of Joule's Law and Ohm's Law, and has nothing to do with the engineer James Watt. Watt experimented with steam locomotives, and died over 20 years before James Joule discovered the equivalence between mechanical and electrical power on which the law is based. Watt's name was adopted after his death as the name of the SI unit of power, and the name of the unit is now used by some electrical practitioners for the formula P = VยทI.
[edit] References
- ^ "Ohm's Law / Watt's Law" from Crown Audio
- ^ Walker, P M B (ed.), Chambers Dictionary of Science and Technology, 1999, ISBN 0550141103. No entry for "Watt's Law".
- ^ Gibilisco, S, The Illustrated Dictionary of Electronics, McGraw-Hill, 8th edition, 2001, ISBN 0071372369. No entry for "Watt's Law".
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