| OCR Text |
Show Why Your Radio lubes Need Filament Light The fact that a radio bulb does emit Ught is entirely an incidental feature of its operation. What is desired in a tube is a flow of little particles of electricity called "electrons," and the easiest way to obtain it is to burn certain kinds of wires in glass bulbs from which the air lias been exhausted. ex-hausted. The temperature must be quite high in order to make the flow copious, and inost wires must be heated white-hot by the current from the A battery for proper operation. Of course, the incandescent in-candescent wire, or "filament," as it is correctly called, emits considerable light, but this phenomenon lias absolutely abso-lutely no connection with the functioning func-tioning of the tube from the radio standpoint. It is quite possible to obtain a stream of the minute electrons in a tube by the use of certain substances known as "radioactive" materials, but their expense and rarity make their practical application extremely limited. limit-ed. Radium and radium compounds are foremost In this radioactive group, so the cost of tubes equipped with filaments of this precious element ele-ment can easily be imagined. No A battery incidentally, would be required re-quired for such tubes, as the How of electrons from radioactive compounds Is automatic and continuous. Certain less expensive chemical compounds of high electron emitting properties have been successfully employed in radio tubes. The wire which ordinarily must be burned at white heat is coated with a layer of one of these compounds, and the tube is then operated at a mere dull cherry-red heat. In many of the modern tubes, of both the coated and uncoated varieties, vari-eties, little or no light Is visible through the glass, because of the inner in-ner coating .of mercury which lines the bulbs. The heaviness of this coaling varies considerably, as will, therefore, the amount of light that penetrates through it, so no significance signifi-cance caa be attached to the brilliance bril-liance of the illumination. |
