Vertical Deflection

no volts
fixed volts
varying volts - Animated GIF
These pictures show how the spot reacts when a voltage is applied to the vertical (Y) deflection plates.

Top Left: With no voltage applied to either set of deflection plates, the spot should be in the center of the screen.

Bottom Left: With a fixed DC voltage applied, the spot will be deflected by an amount proportional to the voltage.

The animation above shows a slowly changing AC voltage.