Resonance is a property of electrical and mechanical systems alike, which each have a ‘natural frequency’, otherwise known as the resonant frequency. This is how the system would vibrate if set in motion and without any subsequent external force.
When we draw graphs of physical phenomena, we often plot time on the horizontal axis. In this graph, known as a Bode (“BOH-dee”) plot, we instead plot frequency on the horizontal axis. This helps us to visualize the output amplitude (size of oscillation) and phase shift (delay of oscillation) for inputs at a given frequency to a dynamic system. In this case, the peak in the top graph corresponds to the resonant frequency
To help interpret this diagram, imagine you are holding a slinky, which dangles freely from your hand. If you move it up and down very slowly (low frequency, left side of axis), its length will not change. If you increase the frequency, the free end will begin to extend more and more, with the maximum extension occurring at the natural frequency. If you move it faster still (right side of axis), the slinky will extend less and less.
When we say we resonate with a person or idea, we are describing the excitation of something within us, an amplification and highlighting which stands out from everything else. Like the mechanical system we just discussed, this sensation does not require an unusual level of effort, it just unfolds with ease.
Learn about the link between resonant frequencies and Bode plots.
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