# Another way to define resonance?

Considering descriptive (and not necessarily applied) physics, would it be proper to define resonance as:

"One of the fundamental means of storing energy" ?

Of course there are other ways to store energy like pressurizing a gas, charging a capacitor or creating chemical bonds for examples.

This wiki article on energy storage doesn't mention resonance anywhere as a means of storing energy, but only briefly when discussing applications it mentions resonance to

.. tune radios to particular frequencies.

In all the examples of resonance I'm able to imagine, resonance 'traps' energy in an object or system, so in a sense the structure of the object or system that enables resonance allows the storage of energy. As one simple example, a mass-spring system stores some initial energy introduced by compressing or extending the spring, and that energy, assuming no dissipative losses flows between potential and kinetic states indefinitely.

Of course there are usually dissipative losses in real resonant systems, but I can think of at least a few examples where the losses are small compared to the systems ability to trap the energy.

I don't believe there are any examples of resonance where energy is not being stored [within the bounds of the system].

• I've never heard resonance described as energy storage and can't see how it would be a particularly useful form of it. It's often not a potential energy; but a cyclic kinetic to potential energy, so there are constant losses during kinetic portions.
– JMac
Commented Feb 11, 2017 at 15:17
• "assuming no dissipative losses" That's a huge and prohibitive assumption when applied to the real world. If we apply your definition to physical materials, it would imply a cyclical deformation of the materials, which would make it a highly inefficient way to "store" energy, since the energy would be quickly lost to heat. Commented Feb 11, 2017 at 15:59
• Ignoring the hypothetical case of zero damping, the proposed definition isn't even true in many situations. Paradoxically, the rate of energy loss from a system when it is resonating is often a maximum not a minimum, because the energy dissipation increases as the amplitude increases. (Of course the rate of energy gain by the system is also a maximum, because of the phase relationship between the motion of the system and the force supplying the energy.) Commented Feb 11, 2017 at 17:22
• @JMac and others: Note I never mentioned the word practical in my question. There is the topic of descriptive physics, apart from applied physics and on the subject of energy we know that it is conserved, that it can flow through space and matter, and that it can be trapped (or stored) either in transient states or indefinitely (in chemical bonds for example). So regarding descriptive physics why can't we say resonance 'stores' energy? Commented Feb 11, 2017 at 20:32
• @alephzero conceptually you don't need a driving force for resonance; a sufficient initial condition will do. Commented Feb 11, 2017 at 20:47