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Do you have a math background in calculus and Laplace transforms? This would be a lot easier to explain if you do. For example, see **broken link removed**.
In a passive circuit (no amplifiers), for ringing to occur in response to a step input, it is necessary but not sufficient that the circuit have an inductor and a capacitor. A circuit with one inductor and one capacitor (and possibly one or more resistors) is a second order system. A passive circuit with two capacitors and resistors is also a second order system, but it will not ring in response to a step input.
i read that resistance causes damping in electric circuits.
so gee..i am confused....:mrgreen:
WHY???
1.am i to understand there is no damping in first order ckts or second order with R and C alone(or R and L alone)?BUT I REALLY DON GET IT...WHY??
Ron's response is very good. But I'm not sure what you do not understand.
We are both assuming that you are talking about damped oscillations. Is this true?
As Ron said, you need to understand the maths. I'll try to explain it without maths.
Take a pure tuned circuit made from a perfect inductor and a perfect capacitor connected in parallel. Now apply a short current pulse to input some energy. The capacitor stores energy in the electric field between its plates and the inductor stores energy in the magnetic field that it creates.
If you start at an instant when all of the energy is stored in the inductor, the energy from the inductor is then transferred to the capacitor, then vice versa.
So the circuit will oscillate for ever with the energy being moved from L to C and then C to L, etc.
Now if you connect a large value resistor (say 1M Ohm) in parallel with the circuit, some of the energy is dissipated as heat in the resistor. Therefore, the system gradually looses energy until all the energy is dissipated. If you looked at the voltage across the circuit with an oscilloscope it would be a damped oscillation. Damping is the gradual loss of energy.
Other examples include a spring with a weight suspended from it. If you pull the weight down (ie. input some energy into the spring) then let it go it will oscillate up and down. The oscillation will be damped because of frictional losses. The energy is being transferred backwards and forwards between the spring and the potential energy of the weight in similar manner to the LC circuit I descrobed above.
Another example is a pendulum.
In all of these cases, there are 2 modes of energy storage eg. L and C, but with an RC circuit, there is only one storage mode, ie. the C.
In the case of the pendulum, the modes are - kinetic energy and potential energy. And energy is lost due to air friction and pivot friction.
I hope this helps. If not feel free to ask more questions.
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