A step down transformer reduces 220V to 11V. The primary draws 5 A current and secondary supplies 90A. Efficiency of the transformer will be:

Foundation

Physics Foundation

EMI

Question

90%

20%

4.4%

33%

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Efficiency of transformer,

$η = \frac{P_{0}}{P_{i}} \times 100 = \frac{I_{S} E_{S}}{I_{P} E_{P}} \times 100 = \frac{11 \times 90 \times 100}{220 \times 5}$

$η$ = 90%