An ideal transformer steps 240 V down to 12 V. When the secondary current is 2.0 A, what is the primary current?
Correct answer D. 0.10 A
Explanation
For an ideal transformer, power in = power out: VₚIₚ = VₛIₛ. So Iₚ = (12 × 2.0)/240 = 0.10 A. Using the voltage ratio the wrong way round gives 40 A.
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