alleryThe power dissipated as heat in a resistor R carrying current I with voltage V across it can be written as
A$P = I^2 R = V^2/R$
B$P = IR = V/R$
C$P = I^2/R = V^2 R$
D$P = I/R^2 = VR$
Answer & Solution
Correct answer: A. $P = I^2 R = V^2/R$
1. Power delivered to the resistor is $P = VI$.
2. Using Ohm's law $V = IR$, substitute $V$: $P = I^2 R$.
3. Substituting $I = V/R$ instead gives $P = V^2/R$.
4. So A is correct; the other forms misuse the dependence on R.
_Source: syllabus Physics Ch 3 "Current Electricity", p.12_
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