A 28-volt generator powers five lamps in parallel: three of 6 ohms and two of 5 ohms. How many amperes will the generator need to supply?

A 28-volt generator powers five lamps in parallel: three of 6 ohms and two of 5 ohms. How many amperes will the generator need to supply?

• A. 25.23 amperes
• B. 20.00 amperes
• C. 30.50 amperes
• D. 18.75 amperes

Answer: (A)

In a parallel setup, the same supply voltage appears across every branch, and the total current is the sum of the currents in each branch. Use I = V/R for each lamp, then add the results. For the three 6-ohm lamps: each draws 28/6 ≈ 4.667 A, so all three draw 3 × 4.667 ≈ 14 A. For the two 5-ohm lamps: each draws 28/5 = 5.6 A, so both together draw 2 × 5.6 = 11.2 A. Total current from the generator = 14 + 11.2 ≈ 25.2 A (about 25.23 A). A quick check using equivalent resistance: 1/Rt = 3/6 + 2/5 = 0.9, so Rt ≈ 1.111 Ω, and I = 28/1.111 ≈ 25.2 A.

In a parallel setup, the same supply voltage appears across every branch, and the total current is the sum of the currents in each branch. Use I = V/R for each lamp, then add the results.

For the three 6-ohm lamps: each draws 28/6 ≈ 4.667 A, so all three draw 3 × 4.667 ≈ 14 A.

For the two 5-ohm lamps: each draws 28/5 = 5.6 A, so both together draw 2 × 5.6 = 11.2 A.

Total current from the generator = 14 + 11.2 ≈ 25.2 A (about 25.23 A).

A quick check using equivalent resistance: 1/Rt = 3/6 + 2/5 = 0.9, so Rt ≈ 1.111 Ω, and I = 28/1.111 ≈ 25.2 A.