1.

A filament bulb (500W, 100V) is to he used in a 230 V main supply. When a resistance R connected in series, it works perfectly and the bulb consumes 500W. The value of R is

Answer»

`26 OMEGA`
`13 Omega`
`230 Omega`
`46 Omega`

SOLUTION :`26 Omega`
Resistance of bulb, `R_(B) = (V^(2))/(P) = ((100)^(2))/(500)`
`therefore R_(B) = 20 Omega`
CURRENT is same in series, therefor , R `prop` V
`therefore(R)/(R_(B)) = (V_(R))/(V_(B))`
`therefore R = R_(B) xx (V_(R))/(V_(B))`
`= 20 xx (130)/(100)`
`therefore R =26 Omega`


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