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In a series L-R circuit, connected with ...

In a series L-R circuit, connected with a sinusoidal ac source, the maximum potential difference across L and R are respectivaly 3 volts and 4 volts.
At an instant the potemtial difference across resistor is 2 volts. The potential difference in volt, across the inductor at the same instant will be:

A

`3 cos 30^(@)`

B

`3 cos 60^(@)`

C

`3 cos 45^(@)`

D

none of these

Text Solution

Verified by Experts

The correct Answer is:
A
In inductor voltage leads by `pi/2` w.r.t current while if is in phase with current in resistors.
`I=I_(0)sinomegat`
`V_(R)=4sinomegat …(1)`
`V_(L)=3 sin (omegat+pi//2)implies V_(L)=3 cosomegat …(2)`
Given that
`2= 4sinomegat implies sinomegat=1/2` or `cosomegat=sqrt(3)/2`
`V_(L)=3xxsqrt(3)/2=(3sqrt(3))/2`
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