A step down transformer converts transmission line voltage from 2200 V to 220 V. Primary coil is having 5000 turns. Efficiency of transformer is 90% and output power is 8 kW. Evaluate number of turns in secondary coil and input power.

Options

A. 9.89 kW
B. 8.89 kW
C. 88.9 kW
D. 889 kW

Answer

B

Explanation

Efficiency of a transfomer is defined as the ratio of output power to the input power.
A transformer which decreases the AC voltage is called a step down transfomer. Transformer is essentially an AC device. It cannot work on DC. A transformer changes AC voltage/currents. efficiency of transformer is given by
`eta=("Output power")/("Input power")=(E_(S)I_(S))/(E_(p)I_(p))`
Here, `P_("output")=8kW,eta=90%`
`P_("input")=(8xx100)/(90)=(80)/(9)kW=8.89kW`