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Formula for Q of resonant circuit?
On 25 Feb 2007 16:40:59 0500, M J Dowden wrote:
I am trying to find the formula used to calculate the Q of a parallel RLC resonant circuit. There are a number of questions in the Amateur Extra test pool[1] that ask this and the formula that I have does not produce the correct answers. I have been using Q = (2 * Pi * f * L) / R, but the questions in section E5G of the test pool don't seem to work with that. The answers that are produced by that formula are among the "distracters," suggesting that I am making an obvious error that they expect some people to make. The formula you used for Q is for a series resonant circuit  call it Qs. For a parallel resonant circuit, you should calculate Q as Qp = 1/Qs. That is, at the end of your calculation, hit the "1/x" key on your calculator. (See also http://en.wikipedia.org/wiki/RLC_circuit) 
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