How long will a lc tank circuit oscillate after power is removed?

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Discussion Overview

The discussion revolves around the duration of oscillation of an LC resonant tank circuit after it has been disconnected from a power source. Participants explore the mathematical and conceptual aspects of oscillation decay, particularly focusing on the time it takes for the oscillations to diminish to a certain level.

Discussion Character

  • Exploratory, Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant inquires about how to determine the length of time an LC tank circuit will oscillate after power is removed, providing specific values for inductance, resistance, and capacitance.
  • Another participant states that the oscillation will decay exponentially and mentions the common practice of specifying the time to reach a certain amplitude ratio, typically 1/e.
  • A further inquiry is made regarding the calculation of the decay time.
  • A participant provides a formula for the time constant related to the quality factor (Q) of the circuit, indicating that Q can be calculated based on circuit losses, specifically mentioning the 500 ohms as the only dissipative losses.
  • A participant expresses appreciation for the information provided.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the specific calculations or values, as the discussion includes inquiries and responses without definitive conclusions.

Contextual Notes

The discussion does not resolve the assumptions regarding the ideality of the circuit or the specific losses involved, which may affect the calculation of the quality factor (Q) and the resulting oscillation duration.

Who May Find This Useful

Individuals interested in the behavior of LC circuits, particularly in the context of oscillation decay and quality factor calculations, may find this discussion relevant.

hobbs125
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If a lc resonant tank circuit is disconnected from power how do you determine the length of time it will oscillate.

L=1 henry, 500 ohms
C=50pf
Fres=22,507 hz
 
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It will decay exponentially. Usually you specify the time it takes to reach a certain ratio of the maximum (usually 1/e or about 36%), since mathematically the amplitude of oscillations will never reach zero.
 
Ok, so how would I calculate that?
 
The time constant is 2Q/frequency; where Q is the quality factor of the circuit.
In order to calculate Q you need to know the losses in the circuit; if the above values are for an ideal circuit (meaning the 500 ohms are the only dissipate losses in the circuit) them you can calculate Q from them (google Q factor)
 
Awesome, thank you.
 

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