Electric circuits with both inductance and capacitance can exhibit natural
oscillations much like a mass suspended from a spring (the inertia is
similar to inductance, the spring similar to capacitance). If there is no
friction in the mechanical system (nor resistance in the RLC circuit), then
a tiny oscillation will continue for ever. In mechanical systems, sometimes
an extra device called a damper is added (such as a shock absorber in a
car's suspension). The whole purpose of such dampers is to dissipate
energy, thus gradually reducing the magnitude of oscillations (e.g. in a car
suspension, you want to dissipate the energy so the magnitude of
oscillations drop off in just a cycle or two).
In circuit analysis, a resistance does the same thing. It will dissipate
the energy of an oscillating circuit and reduce the magnitude of the
oscillations. If you remove all the resistance, it's a lot like removing
the shocks in your car. The least little 'bump' will send it into
oscillations that will continue for many cycles. Some times this is the
desired effect in circuits (deliberate oscillators), sometimes it's not
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