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Electrical and electronics measurements miscellaneous

Electrical and Electronics Measurements

  1. The given figure shows wein bridge connection for frequency measurement. C and R are variables and ganged together. For balanced condition the expression for frequency is ƒ = 1/2πCR when
    1. R1 = R2
    2. R1 = 2R2
    3. R1 = R2/2
    4. R1 = 3R2
Correct Option: C

From the balance equation,

R1R + = R2R.
1
1
jωC
jωCR +
1
jωC

or
R1(jωCR + 1)
=
R2R
jωC(jωCR + 1)

or R1 (– C²ω²R² + 1 + 2 jωCR) = jR2CωR
or 2CωRR1 = CωRR2
∴ R1 =
R2
2

and – C²ω²R² + 1 = 0,
or ω =
1
RC

or ƒ =
1
2πRC



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