Resonance can be produced in a series circuit by varying either L, C, or f.

The general characteristics of a circuit in resonance are the same regardless of which parameter is varied to produce resonance. To summarize:

• The applied voltage is in phase with the current. i.e. The power factor at resonance is 1.
• Power = Impressed Voltage V * Current I
• As the net reactance is zero, so the impedance Z = resistance R. Therefore, the current at resonance is V/R, the maximum possible value for the circuit with its existing elements.