Question

A transformer has an efficiency of 80%. It is connected to a power input of $5kW$ at $200V$ . If the secondary voltage is $250V$ , 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)

$Efficiency=\frac{outputpower}{inputpower}$
Input power $=5000$ W,
Input voltage $=200V$
$\therefore$ Primary current, $I_p=\frac{5000}{200}=25A$
Output power $=5000\times \frac{80}{100}=4000W$
Output voltage $=250V$
Secondary current, $I_s=\frac{4000}{250}=16A$