How do the magnets that redirect the electron beam in the picture tube move it to the exact point that it’s supposed to?
The electromagnets that steer the electron beam are very carefully designed and constructed so that they steer the beam very accurately. They are coils of wire that are built on a form and then glued together so that they cannot move. There are some adjustments made electronically inside the television set to make sure that the beam follows a very start path as it sweeps across the screen. When you adjust the horizontal and vertical sizes of the picture, you are adjusting the currents flowing through these electromagnets.