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Question:

A power transmission line feeds input power at 2300 V to a step-down transformer with its primary windings having 4000 turns, giving the output power at 230 V. If the current in the primary of the transformer is 5 A, and its efficiency is 90%, what is the secondary current?

45 A

25 A

50 A

20 A

Solution:

Powerout = V2I2 = η × Powerin = (90/100) × 2300 × 5
I2 = (90 × 23 × 5) / 230 = 45 A