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A transmission line supplies input power at 2300 V to a step-down transformer whose primary has 4000 turns. The output is delivered at 230 V. If the primary current is 5 A and the transformer's efficiency is 90%, what is the output (secondary) current?

1. 25 A
2. 50 A
3. 35 A
4. 45 A

Correct answer: 45 A

Solution

Input power = Vp * Ip = 2300 * 5 = 11500 W. Output power = efficiency * input = 0.9 * 11500 = 10350 W. Output current Is = output power/Vs = 10350/230 = 45 A.

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