Although
in chemistry a cation is a positively charged ion and an anion is a negatively
charged ion, these prefixes are actually switched when talking about cathodes
and anodes. Ask Mad Physics
How do Televisions and CRT Displays Work? (Printer Friendly)
Unless you are dealing with newer flat-screens (i.e. LCD or plasma displays) your TV, computers, etc. is probably displaying images though a cathode ray tube. These screens work thanks to technology that is not unlike that used in a simple light bulb.
What Does Cathode Mean in Cathode Ray Tube?
Cathodes and anodes are simply terms used in electronics to define terminals: cathode being the negative and anode being the positive. NOTE WELL: For all of you chemistry geeks out there, beware of confusing nomenclature:
Although
in chemistry a cation is a positively charged ion and an anion is a negatively
charged ion, these prefixes are actually switched when talking about cathodes
and anodes.
Why? I don’t know!
Anyway, this is the general premise. So far we know that these tubes work similarly to light bulbs, and have electric poles. How do we find out how they work then?
Well I went to a thrift store and bought myself a color TV (TV is seen left showing the best show ever) for $3.75 and I decided to smash it!
The Wreckage:
Inside the TV there was a lot of circuitry, but one main component, the tube
and the screen. A CRT
monitor
has a tube that sends out electrons similarly to a fluorescent light bulb.
The diagram (right) shows the anode, cathode, conductive coating,
and screen. So far the television has a method by which to beam and soak up
electrons; however, if the TV only used this tube, the image would be one dot
of light. The problem: steering. There are plenty of particles that can be
shot out, but they must be guided to form properly on the screen. This is where
we get our steering coils.
Steering coils (below) are simple windings made out of copper wire. The coil acts as an electromagnet and steers electron beams using magnetic fields. One set of coils controls the vertical motion while another the horizontal. Changing voltage effects the position in the screen.
When
phosphor (the screen) is exposed to radiation, it emits light The radiation
in this case is a beam of electrons. Any fluorescent color is really a phosphor—fluorescent
colors absorb invisible ultraviolet light and emit visible light at a characteristic
color.
Phosphor coats the inside of the screen. When struck by the electron beam it makes the screen glow. In a black-and-white screen, there is one phosphor that glows white when struck. In a color screen, there are three phosphors arranged as dots or stripes that emit red, green and blue light. There are also three electron beams to illuminate the three different colors together. The red, green, and blue (RGB) lights are part of optical physics that show that those three basic colors make up all the others we see. This has been a brief introduction to the technology behind color televisions. There is more that can be studied, but why study when you can smash! Click on the link below to see a slide show of the destruction, and see how many parts you can identify...
Small Slideshow: 240 x 180 (4.5mb MOV)
BIG Slideshow: 720 x 480 (27.6mb MOV)
Cite
Our Experiments & Research
If you have used any of this information or any of these images please
go ahead and cite them in your bibliography. For your convenience, this is
what the citation would look like in MLA format:
Family, Afrooz. “Inside a CRT Monitor .” 27 Mar. 2005 Mad Physics. dd mmm. yyyy †
<http://www.madphysics.com/ask/tv/>
We are glad to share our knowledge with you as long as you cite all of our info, and contact us before you use anything for non-educational purposes (commercial, etc.).
† In the bibliography you must insert the day you visited the site (this is relevant because the site could change at some point), therefore, in the bibliography above replace dd with the day you visited, mmm with the abreviated month, and yyyy with the year (ex: dd mmm. yyyy becomes 23 Dec. 2004).