Reviewed CSCA Physics question · Standard

A 15 V battery is connected to a circuit with a 10 Ω resistor and a 20 Ω resistor in parallel. What is the total current supplied by the battery?

2.25 A
0.50 A
1.50 A
3.00 A

Show the answer and explanation

Correct answer

A. 2.25 A

Principle or equation

For resistors in parallel, the equivalent resistance is 1/R_eq = 1/R1 + 1/R2. Then use Ohm's law I = V / R_eq.

Why this answer is correct

1/R_eq = 1/10 + 1/20 = 3/20, so R_eq = 20/3 Ω ≈ 6.67 Ω. I = 15 / (20/3) = 15 × 3 / 20 = 45/20 = 2.25 A.

Example

With 10 Ω and 20 Ω in parallel across 15 V, total current is 2.25 A.

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