Electron flow in Cathode Ray Tube?

Question

In a TV CRT, electrons from the cathode go pass the anode and strike the TV screen to produce the picture. It seems that, in order to for the system to work, the electrons hitting the screen must be redirected back to the anode to complete the electrical circuit.

I'll like to known how such a circuit is actually done in a CRT.

Philip Wood · Accepted Answer

In the big cathode ray tubes that used to be used in television receivers, the inside of the glass walls leading up to the screen were coated with graphite, and the coat connected to the eht (extra high tension) supply, whose other end was (directly or indirectly) connected to the cathode, so that electrons landing on the screen were returned to source. I believe that in an oscilloscope tube (are they still made?), there's enough natural conductance through the inner glass surface for electrons to find their way back.

Correct answer by Philip Wood on January 2, 2021

Peter R. McMahon · Answer

TV picture tubes and a CRO most CRO tubes, the phosphor on the screen and the inside of the tapered part of the tube are coated with aluminium, which is evaporated on. The electrons can pass through aluminium to the phosphor. Then they are then collected by the coating and returned through the EHT laed, which is clipped into a connector in the side of the tube which is connected to the coating. The graphite on the outside is connected to earth and forms a capacitor with the coating on the inside to save having an expensive high voltage capacitor to smooth the EHT supply. Some CRO tubes have a graphite ring around the inside behind the screen to collect the electrons.

Answered by Peter R. McMahon on January 2, 2021

Electron flow in Cathode Ray Tube?

2 Answers

Add your own answers!

Ask a Question