
420
edge of the screen when the voltage on the final anode is 1000,
raising the anode voltage to 2000 makes it necessary to raise the
deflecting voltage to 200. With magnetic deflection, the angle is
inversely proportional to the square root of the anode voltage; so if,
say, 20 mA in the deflecting coils was sufficient in the first case, it
would have to be raised to only 28.3 mA in the second.
Raising the anode voltage thus necessitates more deflecting
current or voltage, but it brightens the glow on the screen and
generally improves the focus.
For focusing magnetically, it is necessary for the direction of the
field to be along the tube'