Imagine pushing someone on a swing. If you push too early or too late at each return interval, it’s hard to get the swing going. But if you push the swing exactly at its peak, it’s easy to reach higher heights with each push. This perfect timing of pushes is an example of resonant frequency.

Just like the swing, resonant frequency applies to electricity. Achieving resonance during a transfer of power allows the process to be efficient.

An example are LC circuits – L denoting ‘inductor’ and C denoting ‘capacitor’. Inductors are coils that make magnetic fields and capacitors are devices that store and discharge electrical charges. If an inductor and capacitor are arranged in a circuit and are perfectly tuned, the following happens:

• Power flowing through the circuit charges the capacitor. When the capacitor is fully charged, it discharges and supplys power to the coil.
• The power flows through the coil until all the charge from the capacitor is used. During which, the coil produces a magnetic field.
• The magnetic field induces a voltage back through the coil but in the opposite direction. The voltage charges the capacitor back up and the magnetic field fades out just as the capacitor is about to discharge again.
• As the capacitor and coil are resonantly tuned (like the person pushing the swing), the cycle continues over and over. In an ideal scenario, the cycle would continue forever. In reality, other resistive forces eventually bring the cycle to an end.