if the resistance of the bulb is so high it means a tiny current flows in to it , then how does the bulb glow with such a tiny current?
2007-07-26 15:07:14 · 8 answers · asked by sarita s 1 in Science & Mathematics ➔ Physics
Wow. OK, the resistance of the filament ins what "makes it difficult" for the current to pass through. The current overcoming that difficulty is what causes the filament to get hot. The filament glows because it's hot.
It's not that a "tiny current flows in to it", it's that only a tiny current can pass through it. The same current flows "in to" the bulb as flows "in to" your air conditioner.
Remember, 90 percent of the energy used in lighting is given off as heat; 10 percent is light.
2007-07-26 15:14:03 · answer #1 · answered by gabluesmanxlt 5 · 1⤊ 1⤋
The whole idea of an incandescent bulb is to resist the flow of electricity. If the filament were a good conductor, it would remain cold and dark since all the power would just pass through it. By resisting the flow of electricity, a lot of that power is turned to heat, just as the filaments in a toaster heat up and start to glow. The filament of a light bulb will heat up to around 6000F and thus glow with a bright yellow light. The reason it doesn't just burn up is that light bulbs are filled with an inert gas, usually nitrogen but sometimes argon. The lack of oxygen means the filament can't burn since burning would require an oxidant.
2007-07-26 15:46:56 · answer #2 · answered by kevpet2005 5 · 2⤊ 0⤋
It will be brighter if the filament has lower resistance. Power P = V^2/R V = voltage drop across the power source R = resistance P is more if R is less. Note: Those who say that higher resistance will radidate more heat are going by the formula H = i^2Rt (H=heat, i=current,R=resistance,t=time) It seems as if H is more if R is more. But in reality it is not so because i is not a constant. If R changes, then i also changes. Therefore, just because R increases, we should not jump to the conclusion that H will also increase. In household applicances, if you put a bulb in a socket. If you remove that bulb and put another bulb of different resisance, then voltage remains the same. So, we should use the formula P = V^2/R as I have done above.
2016-05-19 21:46:58 · answer #3 · answered by ? 3 · 0⤊ 0⤋
To get light, you have to produce excessive heat.To produce excessive heat in an electrical bulb, you have to design it in such a way that it opposes the current flowing through it.Resistors always oppose the current flow.So the resistence of the filaments of the bulbs are made very high so that enormous heat developes which finally leads to light energy.
2007-07-26 17:19:52 · answer #4 · answered by Arasan 7 · 0⤊ 0⤋
Actually the resistance of a tungsten filament is close to zero when it it is cold. When the switch is turned on there is a sudden surge of current due to this very low resistance, this causes minute damage the the contacts of the switch each time it is operated. Switch manufacturers will ask if the load is a tungsten load in order to properly design the switch for longer life. The tungsten quickly heats up to a glowing condition, it is the heat that increases resistance and extends the life of the filament which is in a partially evacuated environment to reduce the oxygen content of the bulb.
2007-07-30 06:00:58 · answer #5 · answered by johnandeileen2000 7 · 1⤊ 1⤋
The lower the resistance the higher the current flow. A high resistance has a lower current flow so the filament lasts longer.
2007-07-26 15:15:39 · answer #6 · answered by Anonymous · 0⤊ 0⤋
The resistance produces heat. When the filament gets hot enough, it produces light.
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2007-07-26 15:58:41 · answer #7 · answered by Anonymous · 0⤊ 0⤋
its kept high so that the bulb doen'nt burn out, and the tiny current is enough
2007-07-26 15:09:53 · answer #8 · answered by spookydakat 2 · 0⤊ 2⤋