How can the resonance frequency be increased in AC series CKT?

In an AC series resonant circuit, at resonance, the voltage across the capacitor can become very large, even much higher than the source voltage.

Here's Why:

At resonance:

The inductive reactance (XL​) and capacitive reactance (XC​) are equal and opposite:

So they cancel each other out, and the total impedance of the circuit becomes minimum (purely resistive):

The current III in the circuit reaches its maximum:

The voltage across the capacitor is:

Since III is large and XC=1/(2πfC), the resulting VC can be much higher than the supply voltage.

Example:

The capacitor voltage is 628 V, while the source is only 100 V!

Important Notes:

This high voltage is called voltage magnification.

The higher the Q factor of the circuit (low resistance), the greater the magnification:

This is useful in applications like radio tuning, but in power systems, it can cause insulation breakdown if not controlled.

Summary: