Ratio of primary to secondary windings in a step up transformer is 1 : 20. The transformer supplies a current of 2.5 A to a load. If the primary voltage is 220 volt, what is the primary current ?

Secondary voltage Vs=Vp x NsNp=220 x 20 volt=4400 voltPower supplied by the transformer to the load                                    =4400 x 2.5 W=11 kWAssuming 100% efficiency of the transformer, primary current Ip=11 x 103220A=50 A