Question

A capacitor of capacitance 250 pF is connected in parallel with a choke coil having inductance of `1.6 xx 10^(-2) H` and resistance `20 Omega`. Calculate
(a) the resonance frequency and
(b) the circuit impedance at resonance.

Answer 1

a) The resonance frequency of a rejector L-C-R circut is given by
`f=1/(2pi)sqrt(1/(LC) - R^(2)/L^(2))`
`=1/(2pi)sqrt(1/((1.6xx10^(-2))(250xx10^(-12)))-(20)^(2)/(1.6xx10^(-2))^(2))`= `7.96 xx 10^(4) Hz`
b) the circuit impedance at resonance is given by,
`Z=L/(CR) = (1.6 xx 10^(-2))/(250 xx 10^(-12)xx(20))=3.2 xx 10^(6) Omega`