Q. A 220 volt input is supplied to a transformer. The output circuit draws a current of 2.0 ampere at 440 volts. If the efficiency of the transformer is 80%, the current drawn by the primary windings of the transformer is
A) 5.0 ampere
B) 3.6 ampere
C) 2.8 ampere
D) 2.5 ampere
Explanation
[Solution from source] Output power = 440 × 2 = 880 W. Input = 880/0.8 = 1100 W, so primary current = 1100/220 = 5.0 A. Multiplying by 0.8 instead of dividing gives 3.2 A; ignoring efficiency gives 4 A. Answer (1).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.