Q. A step down transformer, transforms a supply line voltage of 2200 V into 220 V. The primary coil has 5000turns. The efficiency and power transmitted by the transformer are 90% and 8 kW respectively. Then the power supplied is
A) 9.89 kW
B) 8.89 kW
C) 88.9 kW
D) 889 kW
Explanation
(b) Efficiency of transformer is given by
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \eta = \frac{Output\ power\ }{Input\ power} = \frac{E_{s}I_{s}}{E_{p}I_{p}}$
Here,$\ P_{output} = 8\ kW,\ \eta = 90\%$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ P_{input} = \frac{8 \times 100}{90} = \frac{80}{9}kW = 8.89\ kW$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.