Which of the following is NOT a valid representation of electrical power P in a circuit? (The current, potential difference and resistance are written symbolically as I, V and R, respectively.)
P = IR²
The electrical power (P) in a circuit can be expressed in several ways, all stemming from Ohm's Law (V = IR), where V is the potential difference, I is the current, and R is the resistance.
- P = VI: This is the most fundamental definition of power, representing the rate at which energy is transferred.
- P = I²R: Substituting V = IR into P = VI gives P = (IR)I = I²R. This shows power is proportional to the square of the current.
- P = V²/R: Substituting I = V/R into P = VI gives P = V(V/R) = V²/R. This shows power is inversely proportional to the resistance.
- P = IR²: This is NOT a valid representation of power. There's no direct relationship between power and the square of resistance alone. Power depends on both voltage and current, or current and resistance, or voltage and resistance, as shown above.
Therefore, the incorrect representation of electrical power is P = IR².
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