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Electric circuits miscellaneous

  1. A series RLC circuit s observed at two frequencies. At ω1 = 1 k rad/s, we note that source voltage V1 = 100 ∠0°V results in current I1 = 0.03 ∠31° A. At ω2 = 2 krad/s, the source volt age V2 = 100 ∠0° V results in a current I2 = 2 ∠0° A. The closest values for R, L, C out of the following options are
    1. R = 50 Ω ; L = 25mH ; C =10μF;
    2. R = 50 Ω ; L =10mH ; C = 25μF;
    3. R = 50 Ω ; L = 50mH ; C = 5μF;
    4. R = 50 Ω ; L = 5mH ; C = 50μF;
Correct Option: B


at ω2 = 2000 r/sec

φ = 31° ⇒ tan-1
XL - XC
R

⇒ tan31° =
XL - XC
R

tan31° = ω1L -
1
ω1C
    R

ω1L -
1
= 0.600 × 50
ω1C

ω1L -
1
= 30.04 q ......(1)
ω1C

ω2L -
1
= 0 ......(2)
ω2C

ω1 = 1000 r / sec ;
ω2 = 2000 r / sec
from 1 and 2, C = 25 μF
L = 10 mH



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