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 amp, the efficiency of the transformer is approximately

Answer»

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

SOLUTION :Given : Output power P = 100 W
Voltage across PRIMARY `V_(P)=220 V`
CURRENT in the primary `I_(P)=0.5 A`
Efficiency of a TRANSFORMER, `eta = ("Output power")/("Input power")xx100`
`=(P)/(V_(P)I_(P))xx100=(100)/(220xx0.5)xx100=90%`


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