1.

Derive an expression for resonant frequency of series circuit containing inductor, capacitor and resistor.

Answer»

SOLUTION :
Series LCR circuit is said to be in resonance when CURRENT through the circuit is maximum. In a series LCR circuit current amplitude is given by
`i_(m)=(V_(m))/(Z)`
`i_(m)=(V_(m))/(sqrt(R^(2)+(X_( C )-X_(L))^(2)))`
where `X_( C )=(1)/(omegaC)` and `X_(L)=omega_(L)`
If FREQUENCY is varied, at particular angular frequency `omega_(0)` the condition
`X_( C )=X_(L)` is achieved, this condition is called resonance, `(1)/(omega_(o)C)=omega_(0)L`
`:." "omega_(0)=(1)/(sqrt(LC))`
`2pi v_(o)=(1)/(sqrt(LC))""(because omega_(0)=2pi v_(0))`
`v_(0)=(1)/(2pi sqrt(LC))` is called resonant frequency


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