A `220 V` input is supplied to a transformer. The output circuit draws a current of `2.0 A` at `440 V`. If the efficiency of the transformer is `80%`, the current drawn by the primery winding of the transformer is

Options

A. 3.6 ampere
B. 2.8 ampere
C. 2.5 ampere
D. 5.0 ampere

Answer

D

Explanation

Here
Input voltage, `V_(p)=220V`
Output voltage `V_(s)=440V'`
Input current `I_(p)=?`
Output current `I_(s)=2A`
Efficiency of the transformer `eta=80%`
Efficiency of the transformer,
`eta=("Output power")/("Input power")` or `eta=(V_(s)I_(p))/(V_(p)//I_(p))`
or `I_(p)=(V_(s)I_(s))/(etaV_(p))=((440V)(2A))/((80/100)(220V))`
`=((440v)(2A)(100))/((80)(220V))=5A`