Newnes Dictionary of Electronics

Q

Q factor Of an inductor or capacitor the ratio of its reactance to its effective series resistance. An ideal inductor or capacitor has no series resistance and the Q factor is therefore infinite. Practical components inevitably have resistance and thus Q factors are finite: they are, in fact, a figure of merit indicating the extent to which the component approximates to a pure reactance. For inductors Q values of 100 to 300 are possible and for capacitors much higher values are common. For an inductor Q is given by Lω/R and for the capacitor 1/ωCR.

quadraphony In sound reproduction an extension of the stereo principle, in which two further channels are used to originate stereo sound behind the listener to give the illusion that he is surrounded ...