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The power factor of an R-L circuit is 1/...

The power factor of an R-L circuit is 1/`sqrt 2` if the frequency of AC is doubled , what will be the power

A

`1/sqrt 3`

B

`1/sqrt(7)`

C

`1/sqrt 7`

D

`1/sqrt 11`

Text Solution

Verified by Experts

The correct Answer is:
B
Power factor ,cos`phi` = `1/sqrt 2 = R / sqrt R^(2) + omega^(2)(L)^(2)`
This gives , `omegaL = R`
when `omega` is doubled , we find
`cosphi^(')= R/sqrt R^(2) + 4omega^(2)L^(2)` =`R/sqrt R^(2) + 4R^(2)` = `1/sqrt 5`
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