A transformer having efficiency of 90% is working on 200 V and 3 kW power supply. If the current in the secondary coil is 6 A, the voltage across the secondary coil and the current in the primary coil respectively are

Here, Efficiency of the transformer, η=90%Input power, Pin=3 kW = 3×103W=3000 WVoltage across the primary coil, Vp=200VCurrent in the secondary coil, Is=6AAs Pin=IpVp∴ Current in the primary coil,Ip=Pin Vp=3000 W200 V=15 Aη=PoutPin=VSIsVpIp∴  90100=6Vs3000 or Vs=90×3000100×6=450 V