The classic example is comparing an LC circuit to a mass spring system, or
an RLC circuit to a damped mass spring system. They both share essentially
the same differential equations, which is why people often compare them.
You can apply these to a small-angle approximated pendulum as well
(anything in simple harmonic motion).
So while there isn't really 'kinetic energy' to talk about in LC, the
mathematical equivalent in the LC circuit to KE in a mechanical system is
energy stored in the magnetic field of the inductor. However, the choice is
NOT arbitrary.
In short:
Potential Energy (Grav or Spring) to Kinetic Energy is analogous to:
Potential Energy (in capacitor) to Energy stored in a magnetic field
(Inductor).
You can refer to these for the differential equations which should be quite
enlightening:
http://www.ctaps.yu.edu.jo/physics/Courses/Phys102/Phys102_Web_Resources/RCV/LC_Oscillator.htmhttp://physics.bu.edu/~duffy/sc545_notes05/LC_math.html;
On Fri, Apr 25, 2014 at 10:24 AM, David Speck <Dave@xxxxxxxxxxxxxxxx> wrote:
> Jim,
>
> It's neither. The L and C are containers for the energy, which is in the
> form of electrical current alternating with electrical potential (voltage).
>
> In a gravity pendulum system, the energy oscillates between being all
> kinetic and all potential energy. The interaction between the mass of the
> pendulum and gravity are the containers for the energy of the system.
>
> When the pendulum is at the top of the swing at either end, all of the
> energy is potential, because, for just that moment, the pendulum is not
> moving. It has to be moving to have kinetic energy. At the very bottom of
> the swing, the energy is all kinetic, because the pendulum can't fall any
> further. Thus it has no potential energy at the very bottom of the swing.
> The pendulum has to be able to fall further to have any potential energy.
>
> In a perfect parallel LC circuit with no resistance, the current sloshes
> back and forth between + at the top, and - at the bottom at one end of the
> cycle, to - at the top and + at the bottom, reversing the polarity at the
> opposite side of the cycle, in a classic sinusoidal fashion.
>
> When the voltage reaches the maximum, at the top of the sine wave, all the
> energy is potential, 'cause no current is flowing. When current is at
> maximum, as the voltage curve crosses the zero voltage level, all energy is
> kinetic, as there is no potential difference across the tank.
>
> HTH,
>
> Dave
>
>
> On 4/25/2014 7:46 AM, Jim wrote:
>
>> I've heard of LC circuits being compared to pendulums. Is there kinetic
>> and potential energy involved? If so, which is kinetic, the Inductor?
>> Thank you,
>> Jim
>>
>
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--
Thanks!
Guangyan
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