3-37The voltage at the center and the ends varies at a sinusoidal rate between the limits shown. At theone-fourth the three-fourths points, the voltage is always zero. A continuous series of diagrams such asthese is difficult to see with conventional test equipment, which reads the effective or average voltageover several cycles. The curve of amplitude over the length of line for several cycles is shown in figure3-29, view B. A meter will read zero at the points shown and will show a maximum voltage at the center,no matter how many cycles pass.As shown in view D, the amplitude varies along the length of the line. In this case it is zero at theend and center but maximum at the one-fourth and three-fourths points. The entire diagram of the open-ended line conditions is shown in view E. The standing waves of voltage and current appear together.Observe that one is maximum when the other is minimum. The current and voltage standing waves areone-quarter cycle, or 90 degrees, out of phase with one another.REFLECTION OF AC VOLTAGE FROM A SHORT CIRCUITReflection is complete when an rf line is terminated in a short circuit, but the effect on voltage andcurrent differs from the effect obtained in an open-ended line. Voltage is reflected in opposite phase,while current is reflected in phase. Again look at the series of diagrams in figure 3-27. The left columnrepresents current, and the right column shows voltage changes on the shorted line. The standardrepresentation of standing waves on a shorted line is shown in figure 3-30; the voltage is a solid line, andWKH FXUUHQW LV D GDVKHG OLQH 7KH YROWDJH LV ]HUR DW WKH HQG DQG FHQWHU DQG PD[LPXP DW WKH DQGSRLQWV ZKLOH WKH FXUUHQW LV PD[LPXP DW WKH HQG DQG FHQWHU DQG PLQLPXP DW WKH DQG SRLQWV Figure 3-30.—Standing waves on a shorted line.As we discussed voltage and current waves on transmission lines, we pointed out several differencesbetween open and shorted lines. Basic differences also appear in the standing-wave patterns for open andshorted lines. You can see these differences by comparing figure 3-29, view E, and figure 3-30. Noticethat the current and voltage standing waves are shifted 90 degrees with respect to the termination. At theopen end of a line, voltage is maximum (zero if there are no losses in the line). At a short circuit, currentis maximum and voltage is minimum.Q23.Two types of waves are formed on a transmission line. What names are given to these waves?

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