A transformer of efficiency 90% draws an imput power of 4kw. An electrical appliance connected across the secondary draws a current of 6A. The impedance of the device is

Options

A. `60 Omega`
B. `50 Omega`
C. `80 Omega`
D. `100 Omega`

Answer

D

Explanation

`eta= (output power)/(I nput power)=(V_SI_S)/4000= (Z(I_S)^2)/4000`
`therefore 90/100= (Z(6)^2)/4000`
or `Z= 100 Omega`