R
L
S
C
Figure 39.3: An LCR circuit.39.2 LCR Circuits.
If a resistor is placed in an LC circuit, we have anLCR circuit(Fig. 39.3). The effect of the resistor is to
introduce damping into the oscillation of the circuit: while an LC circuit oscillates like a simple harmonic
oscillator, an LCR circuit behaves like adampedharmonic oscillator. Depending on the value of the resistance
R, the current in the circuit may be underdamped, overdamped, or critically damped, just as with the damped
harmonic oscillator.