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In the latter the impedance enters prominently into play as the frequency is increased, but the gas acts much as a series of condensers would: the facility with which the discharge passes through seems to depend on the rate of change of potential.
The things needed are an arc-lamp, an impedance coil, or small transformer- coil, a rheostat, and a source of energy. The alternating current is not adapted to reproduce speech, but the ordinary direct current is. Of course, the theory isn't half as simple as the apparatus I have described." He had unscrewed the Osram lamp. The talking ceased immediately.
When sounds vibrate the ribbon extremely low alternating voltages are developed at the ends of the ribbon, which has a very low impedance of only 0.15 ohm, necessitating the use of a step-up transformer of 1:45 turns ratio very close to it. The frequency response is 20 to 16,000 Hz.
Where a wire is wound in a coil the impedance of the circuit is increased and where an alternating current is used the impedance grows greater as the frequency gets higher. The impedance of the magnet coils of a receiver is so great for high frequency oscillations that the latter cannot pass through them; in other words, they are choked off. How the Headphones Work.
Here the gas might only act as a conductor of no impedance diverting the current from the wire as the impedance of the latter is enormously increased, and merely heating the ends of the wire by reason of their resistance to the passage of the discharge.
Where a wire is wound in a coil the impedance of the circuit is increased and where an alternating current is used the impedance grows greater as the frequency gets higher. The impedance of the magnet coils of a receiver is so great for high frequency oscillations that the latter cannot pass through them; in other words, they are choked off. How the Headphones Work.
He could make quite an issue out of the need to determine the characteristic impedance of their sky. That might even be interesting, at that; would it be anywhere near 300 ohms here? But it seemed that stalling wasn't going to work. They'd given him what they expected him to need, and he'd have to be careful to need only what they expected, or they might just decide he wasn't Dave Hanson.
When a current is flowing through a circuit the material of which the wire is made not only opposes its passage this is called its ohmic resistance but a counter-electromotive force to the current is set up due to the inductive effects of the current on itself and this is called impedance.
If a ground connection is made it can only be made through a conductor offering an enormous impedance, or though a condenser of extremely small capacity. This, however, does not do away with other difficulties.
Where two or more headsets are used with one wireless receiving set they must all be of the same resistance and connected in series, that is, the coils of one head set are connected with the coils of the next head set and so on to form a continuous circuit. The Impedance of Headphones.
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