Question

A transformer is employed to reduce 220 V to 11 V. The primary draws a current of 5 A and the secondary 90 A. The efficiency of the transformer is

• A. 20%
• B. 40%
• C. 70%
• D. 90%

Answer 1

Answer: (D)

90%

Answer 2

$\eta = \frac{V_{s}i_{s}}{V_{p}i_{p}} \times 100 = \frac{11 \times 90}{220 \times 5} \times 100 = 90\mspace{6mu}\%$