1.

240 A.C. mains supply is given to one transformer which draws 0.7 A from it. This transformer is used to operate a bulb having power rating "24 V, 140 W". Then efficiency of this transformer is ......

Answer»

`90%`
`80%`
`70%`
`60%`

Solution :INPUT POWER `P_1=VI=240xx0.7`
`therefore` input power `P_1`= 168 W
output power `P_2`= 140 W
`therefore` EFFICIENCY of transformer
`=("Output power" (P_2))/("Input power" (P_1))=140/168xx100` = 80%


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