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Mechanical Properties Of Fluids

Question
CBSEENPH11020789

A transistor-oscillator using a resonant circuit with an inductor L (of negligible resistance) and a capacitor C in series produce oscillations of frequency f. If L is doubled and C is changed to 4C, the frequency will be

  • f/4

  • 8f

  • straight f divided by 2 square root of 2
  • f/2

Solution

C.

straight f divided by 2 square root of 2

In a series LC circuit, frequency of LC oscillations is given by
                        straight f space equals fraction numerator 1 over denominator 2 straight pi square root of LC end fraction
or           straight f proportional to fraction numerator 1 over denominator square root of LC end fraction
rightwards double arrow space space space space space straight f subscript 1 over straight f subscript 2 space equals space square root of fraction numerator straight L subscript 2 straight C subscript 2 over denominator straight L subscript 1 straight C subscript 1 end fraction end root
  Given comma space space space straight L subscript 1 space equals space straight L comma space space straight C subscript 1 equals straight C comma space space straight L subscript 2 space equals space 2 straight L comma space space straight C subscript 2 space equals space 4 straight C comma space space straight f subscript 1 space equals space straight f
therefore space space space space space straight f over straight f subscript 2 space equals space square root of fraction numerator 2 straight L space cross times space 4 straight C over denominator LC end fraction end root space equals space square root of 8
rightwards double arrow space space space space space space space straight f subscript 2 space equals space fraction numerator straight f over denominator 2 square root of 2 end fraction