alleryStart learning →Of the three power expressions, which one holds for any device and not only for resistors?
AP = I times V
BP = V squared / R
CP = I squared / R
DP = I squared R
Answer & Solution
Correct answer: A. P = I times V
1. P = I V follows straight from energy being charge times voltage, with no assumption about the device.
2. The other two forms are reached by substituting Ohm's law, which needs a resistance to substitute.
3. So P = V squared / R and P = I squared R apply only to resistors.
4. For a motor, a battery being charged or a non-ohmic device, only P = I V can be trusted.
5. P = I squared / R is not one of the three valid forms at all and is included as a dimensional trap.
_Source: OpenStax College Physics (CC BY 4.0), Ch 20 "Electric Current, Resistance, and Ohm's Law", section Power in Electric Circuits_
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