The power dissipated in a resistor can be written as
- A. I squared R, VI, or V squared over R
- B. IR only
- C. V squared R
- D. I over R
Explanation
All three forms follow from P equals VI combined with Ohm's law, and which one is most convenient depends on what the question gives you. Use I squared R when the current is fixed, as in a series circuit, and V squared over R when the voltage is fixed, as in parallel household wiring. Note that for fixed voltage a smaller resistance dissipates more power, which surprises many students.