Three defrost heaters, each 15 ohms, are wired in parallel to a 120 volt power supply. How many watts are consumed?

Three defrost heaters, each 15 ohms, are wired in parallel to a 120 volt power supply. How many watts are consumed?

• A. 2880
• B. 960
• C. 3600
• D. 1800

Answer: (A)

In a parallel setup, each heater gets the full supply voltage, so each one draws current and uses power based on 120 V across 15 Ω. For one heater: current = 120 V / 15 Ω = 8 A, power = V × I = 120 × 8 = 960 W. With three heaters in parallel, total current = 3 × 8 A = 24 A. Total power = V × I_total = 120 × 24 = 2880 W. Equivalently, the combined resistance in parallel is 15 Ω / 3 = 5 Ω, so total power = 120^2 / 5 = 2880 W. So the total power consumed is 2880 watts.

In a parallel setup, each heater gets the full supply voltage, so each one draws current and uses power based on 120 V across 15 Ω.

For one heater: current = 120 V / 15 Ω = 8 A, power = V × I = 120 × 8 = 960 W.

With three heaters in parallel, total current = 3 × 8 A = 24 A. Total power = V × I_total = 120 × 24 = 2880 W.

Equivalently, the combined resistance in parallel is 15 Ω / 3 = 5 Ω, so total power = 120^2 / 5 = 2880 W.

So the total power consumed is 2880 watts.