A transformer is used to illuminate a bulb of ( 36W and 12 V ) with the help of 220 volt mains. If the efficiency of the transformer is 75%, then current in primary coil is

A step-down transformer is used on a 1000 V line to deliver 20A at 120V at the secondary coil. If the efficiency of the transformer is 80% the current drawn from the line is.

A transformer is used to light a 100 W and 110 V lamp from a 220V mains. If the main current is 0.5 A , the Efficiency of the transformer is approximately: