Question

A transformer has an efficiency of 80%. It is connected to a power input of $ 5 \,kW $ 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
• E. 40 A, 16 A

Answer 1

Answer: (C)

$ Efficiency=\frac{output\text{ }power}{input\text{ }power} $
Input power $ =5000\text{ } $ W,
Input voltage $ =200\text{ }V $
$ \therefore $ Primary current, $ {{I}_{p}}=\frac{5000}{200}=25\,A $
Output power $ =5000\times \frac{80}{100}=4000W $
Output voltage $ =250\text{ }V $
Secondary current, $ {{I}_{s}}=\frac{4000}{250}=16\,A $