what i know about curves is tht if no voltage was supplied the graph would be a stright line parallel tothe x axis.. but if dc current were to be supplied, then a same graph is produced but with different position (up or down) depending on the postion of the postive charge plate..eg: if postive plates was up and a dc current is supplied so the beam of electron would only deflect on tht side, hence the graph would be same as zero voltage but in different position depending on the beams, deflection.
when an AC current is supplied the postive charge changes its position so the beam of electron deflects in different direction continuosly thus causing a sine curve(up and down, up and down..etc)
this would have the same effect with time base on ,cuz here the position of charge does not change, the amount of voltage changes but i think it would have the same effect as as, excep it would be steepr and sharper turns..