Q. A transformer has an efficiency of 80%. It is connected to a power input of 5kW at 200 V. If the secondary voltage is 250 V, the primary and secondary currents are respectively
A) 25 A, 20 A
B) 20 A, 16 A
C) 25 A, 16 A
D) 40 A, 25 A
Explanation
(c) Efficiency $= \frac{Output\ power}{Input\ power\ }$
Input power=5000 W
Input voltage=200 V
$\therefore$ primary current, $I_{p} = \frac{5000}{200} = 25\ A$
Output power $= 5000 \times \frac{80}{100} = 4000\ W$
Output voltage =250 V
Secondary current, $I_{s} = \frac{4000}{250} = 16\ A$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.