Description:
We study how the reactance Z of a parallel RLC circuit changes with driving frequency ω. We found that in the case that no resistor is connected to the L and C, there is a maximum Z appears at the same ω while the Z approaches to zero when ω→0 and ω→∞. However, in the case that a resistor is connected to the L and C respectively, a maximum or a minimum of Z can appear depending on ω/ω0 where ω0=1/ LC .