2007-04-12 23:03:12 · 10 answers · asked by siva 1 in Science & Mathematics ➔ Physics
When you heat something, it gives off "black body radiation" whose color is characterized by its temperature. The sunlight's color (effective) temperature, after passing through the atmosphere, is 5000K. You'd have to heat something that hot for it to emulate sunlight (if you used heat at all). Nothing solid can get that hot. Tungsten is the closest metal. Carbon is higher, but it's too weak at high temperatures to make a strong filament.. House lights generally run at about 2500K. The melting point is higher, but the hotter you get the metal (by Ohmic heating), the faster it will sublime (turn to vapor directly from solid). The dark stuff you see coating the insides of old unfrosted light bulbs is recondensed Tunsten.
2007-04-13 02:53:27 · answer #1 · answered by Dr. R 7 · 0⤊ 0⤋
tungston is a resistance wire , such wires tend to grow very hot when current passes through them, therefore this filament(tungston) grows white and gives out light when an electrical current is flowing.
2007-04-13 06:21:10 · answer #2 · answered by Loiwah C 1 · 0⤊ 0⤋
Tungsten is used in electric bulbs because it has an extremely high melting temperature (~3,695 K) and a low vapour pressure at high temperatures, resulting in more luminosity combined with a long lifetime
2007-04-13 06:43:43 · answer #3 · answered by superbparee 1 · 0⤊ 0⤋
Tungsten has a high melting point and hence is the material of choice for electrical filaments, welding electrodes etc., with only one restriction, viz. its poor oxidation resistance requires either vacuum or inert gas atmosphere. High temperatures are needed for better efficiency in emission of light.
2007-04-13 06:56:25 · answer #4 · answered by Swamy 7 · 0⤊ 0⤋
In electric bulbs the color is a function of the temperature. So the only reason to use one material instead of an other is the longevity of the material
2007-04-13 06:32:22 · answer #5 · answered by Anonymous · 0⤊ 0⤋
tungston is a good electron emmitor , its work function is also low and its melting point is very high.
2007-04-13 06:23:04 · answer #6 · answered by Kena P 2 · 0⤊ 0⤋
Tungsten's melting point is something like 4,000 degrees. Thus, it can be heated to white-hot for thousands of hours without breaking. That makes it a fantastic metal to use for filaments.
2007-04-13 06:11:04 · answer #7 · answered by poorcocoboiboi 6 · 0⤊ 0⤋
because it have a high melted point and a good reflection with warming and cooling
2007-04-13 06:08:45 · answer #8 · answered by suerena 2 · 0⤊ 0⤋
its melting point is very high ... therefore it can allow heat to pass without melting itself
2007-04-13 06:39:37 · answer #9 · answered by harshad 2 · 0⤊ 0⤋
because that withstands a lot of heat and can be trimmed to a thin filament...
2007-04-13 06:07:46 · answer #10 · answered by sathya 2 · 0⤊ 0⤋