Question

A step-down transformer is used on a `1000 V` line to deliver `20A` at `120V` at the secondary coil. If the efficiency of the transformer is `80%` the current drawn from the line is.
A. `3A`
B. `30A`
C. `0.3A`
D. `2.4A`

Answer 1

Correct Answer - A
`eta=(P_(S))/(P_(P))=(I_(S)*e_(S))/(I_(P)*e_(P))`
`I_(P)=(I_(S)*e_(S))/(eta*e_(P))=(20xx120)/(0.8xx1000)=3A`