2007-01-24 20:54:49 · 5 answers · asked by noob 1 in Science & Mathematics ➔ Physics
As the electric current flows through the filament some of the electrons collide with the atoms of the filament, causing a little light, and a lot of heat. As the filament gets hotter, the atoms vibrate more and more, causing the resistance of the filament to increase. This causes more and more electrons to collide with more and more of the atoms, thus causing even more heat. That's why the filament of a bulb glows white hot and generates light and a lot of heat, and why the resistance increases as it gets hotter.
A light bulb is effectively a 'positive temperature dependent resistor'. Not all materials increase their resistance as they get hotter, some reduce it instead, for example a negative temperature dependent resistor.
2007-01-25 00:28:50 · answer #1 · answered by Timbo 3 · 0⤊ 0⤋
Most metals exhibit a "positive" temperature coefficient, meaning the resistance increases when temperature increases. Tungsten is no exception. Although a dimmer can "change the resistance" of a lamp filament, it only does so indirectly. It does this by reducing the average applied voltage by "pulsing" it. It runs cooler, less light emitted. Thus as it doesn't get so hot, its average resistance will be lowered as a matter of course.
2016-03-29 01:38:10 · answer #2 · answered by Anonymous · 0⤊ 0⤋
The current in the wire is due to the drift velocity of the free electrons in the wire.
The free electrons are at random motion even when there is no current.
That is they do have kinetic energies, The average kinetic energy of the electrons is the indication of the temperature.
When the temperature of the wire is increased, the kinetic energies of these free electrons are increased.
Therefore more energy is required to have the drift velocity which is current.
That is the resistance of the wire is increased.
2007-01-24 21:21:28 · answer #3 · answered by Pearlsawme 7 · 0⤊ 0⤋
electrons and atoms are moving too fast for co-ordinated charge transfer between atoms. It's like in that Olympic sport where runners pass the stick to each other. If the receiving runner was to wiggle around and move his arm around while the first runner was trying to hand it over to him. It's harder to place it in his hand.
2007-01-24 21:13:02 · answer #4 · answered by sandwreckoner 4 · 0⤊ 0⤋
you guys are geeks...
2007-01-24 21:36:55 · answer #5 · answered by jimmy 1 · 0⤊ 1⤋