1.

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

Answer»

`50%`
`90%`
`10%`
`30%`

Solution :Here `V_(p) = 220 V, V_(s) = 110 V, I_(p) = 0.5 A` and POWER output 100 W
`therefore` Power input `=V_(p)I_(p) = 220 XX 0.5 = 110 W`
`therefore` Efficiency of TRANSFORMER `=("output")/("input") = 100/110 xx 100% = 90%` (APPROX)


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