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Voltage Distribution on a Short-Circuited Lossless Line

When an electromagnetic wave strikes the distant end of a short-circuited line, the voltage component must become zero because voltage cannot exist across zero impedance. For this to happen, it is necessary that a 180° phase shift of the electric field and voltage component of the electromagnetic wave occur at the short-circuited end of a line. Then, the reflected voltage component will cancel the oncoming initial voltage component, and the resultant electric field and the voltage will be zero. A short circuit provides a conducting path so that the electric charges, on which the electric lines of force terminate, can flow from one wire to the other.

If the waves are studied at several instantaneous values of the applied generator voltage, Fig. 7 results. The various waves are combined as for Fig. 6, with the 180° angle caused by the phase reversal taken into consideration. Voltmeters connected along the line would give readings as indicated by Fig. 7(e), which is the "voltage standing wave", on a short-circuited lossless line. It will be noted that the voltage at the distant end always is zero, as it must be for the short-circuited line.



Last Update: 2011-05-18