 # What are resonance and resonant frequency

Under periodic external force, when the frequency of external significance is the same as or very close to the natural oscillation frequency of the system, the phenomenon that the amplitude increases sharply is called resonance. The frequency at which resonance occurs is called “Resonant frequency”.

At resonance, the driving function (force, voltage, etc.) is strictly opposed by the system’s dissipative process (mechanical loss, electrical loss, etc.).

For a piezoelectric transducer, “resonance” is sometimes used to indicate series resonance or short circuit resonance. To avoid confusion, the use of “resonance” in this context should be avoided.

• The inductor and capacitor series circuit’s resonance is called “series resonance” or “voltage resonance”.
• The parallel circuit of inductor and capacitor’s resonance is called “parallel resonance” or “current resonance”.

### The difference between resonant frequency and natural frequency

Is the Resonant frequency the same as the natural frequency?

From a numerical point of view, they are equal. But the concepts of the two are not the same.

When a device is formed, its vibration frequency is fixed, and this frequency is the natural frequency. The natural frequency is related to its hardness, quality, and external dimensions and generally does not change.

The natural frequency is a fixed vibration frequency unique to a particular substance. We know that every sense vibrates. But because of the difference of microscopic particles in matter, the frequency of each case is different.

Under the action of an external force of a specific frequency, a substance vibrates at the external force-frequency, which is called forced vibration in physics. But because it consumes energy, the amplitude of the forced vibration becomes smaller. When the external force’s frequency is the same as the natural frequency of the substance, the amplitude will reach its maximum. That is, resonance occurred!

The condition for resonance is that the applied frequency is equal to the natural frequency of the object.