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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
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- R1 = R2
- R1 = 2R2
- R1 = R2/2
- R1 = 3R2
Correct Option: C
From the balance equation,
R1 | R + | = R2 | R. | ||||
jωC | |||||||
jωC | R + | ||||||
jωC |
or | = | |||
jωC | (jωCR + 1) |
or R1 (– C²ω²R² + 1 + 2 jωCR) = jR2CωR
or 2CωRR1 = CωRR2
∴ R1 = | |
2 |
and – C²ω²R² + 1 = 0,
or ω = | |
RC |
or ƒ = | |
2πRC |