Question

At resonance, what is impedance of a series RLC circuit?

a. It depends on many other considerations, such as the values of L and C.
b. less than R
c. equal to R
d. larger than R
Which of the following does the quality factor of the circuit depend on? (Select all that apply.)
a. C
b. the width of the resonance
c. L
d. R

Answer 1

c) Equal to R

b) the width of the resonance

Explanation: In general the impedance Z of an electrc circuit is:

Z = R + jX

Now when the circuit is capacitive, the above mentioned relation become Z = R + 1/jwc where ( w = 2πf )

And when the circuit is inductive Z becomes

Z = R + j wl

Resonance condition implies that the reactance created by capacitors are equal at the inductances produced by inductors, in other words the circuit will behaves as it were resistive.

The impedance will be equal to R

The Q factor is[

Q = X/R in which X is the module of either the capacitive or inductive reactance.

Q has an inverse relation with the band width.