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The filament inside is heated. Once it gets hot enough, it dissipates some of the energy as heat and light.
Hot, really hot. Typically in the range of about 2000C to 2500C (3600F - 4500F). It would be pretty difficult to directly measure the temperature …of the filament so you have to use something other than a thermometer for the measurement. It should be possible to estimate the temperature of the filament from the light spectrum. Basically, treat the light bulb like a perfect black body radiator and use Plank's Law (http://en.wikipedia.org/wiki/Planck%27s_law) and the light spectrum of the bulb (for example http://www.graphics.cornell.edu/online/measurements/source-spectra/index.html) to calculate the temperature. Another way, which is a bit easier, is to use basic electronic theory to calculate the temperature of the filament that is required to produce the manufacturer's specifications for the bulb. For example, consider a typical 100 watt, 120 VAC light bulb with a tungsten filament. The bulb consumes (and radiates) 100 watts of power. A light bulb is a purely resistive load so Power=(Voltage)*(Current). Plugging in 100 watts as the power, 120 as the voltage (actually, that's the RMS voltage), and solving for current we get an RMS current of 0.83 amps. Since the bulb is just a resistor it obeys Ohm's Law; Voltage=(Current)*(Resistance). Our voltage is 120 and we determined the current to be 0.83 amps, so the resistance of the bulb when it is operating is 120/0.83= 144 ohms. If you take a 100W incandescent light bulb and measure its resistance at room temperature you get a value of about 15 Ohms. The difference between the room temperature resistance and the resistance when the bulb is operating is due to the affect of temperature on the filament's resistance. Metals (and conductors in general) increase their resistance as they are heated. The resistance at a particular temperature can be calculated with; R=Rref*(1 + alpha(T-Tref)] Where, R is the resistance at temperature T degrees Celsius. Rref is the resistance at a standard temperature Tref (often 0C or 20C). Alpha is the "temperature coefficient of resistance" for the material. For tungsten alpha=0.0044/C with a Tref of 20C (68F). If we assume that the 15 Ohm resistance at room temperature is close enough to the value at 20C (68F) then we can use Rref=15 ohms and R is the 144 ohms we calculated from the wattage and voltage of the bulb. Plugging these numbers into the equation; 144=15*(1 + 0.0044*(T - 20)) Solving for T (the temperature required to get the filament's resistance to 144 ohms) we get T=1975C (about 3600F). That's pretty hot! The filaments temperature will change if the applied voltage changes. The temperature will also be different from light bulb to light bulb (even if they have the same voltage and wattage ratings) since no two bulbs are exactly alike. An individual bulb will also change as it ages and as a function of the temperature outside the bulb.
The filament in incandescent bulbs are made out of tungsten, a very resistant element. Published by: Rashitha Gamage
Electric lamps having incandescent filaments.
Current passing through a special wire like tungsten heat up the wire and create light by emitting photons
An incandescent bulb.
An incandescent light bulb works by putting so much current through the filament that the filament glows white hot. You risk serious heat burns from any incandescent bulb that… is still switched on.
Usually a Tungsten alloy.
Most common house hold light bulbs are really just evacuated to really low pressures and contain a tungsten filament. the reason being is that tungsten has high resistivity an…d low corrosive properties. they used to use carbon in the beginning. the reason for the vacuum is to prevent evaporation of the filament. Argon Usually they are filled with an inert gas such as nitrogen and others are filled with a gas containing low pressure mercury vapour and argon, xenon, neon or krypton. An inert gas such as Argon
A filament lamp.
Filaments in incandescent bulbs are usually around 3000º C or 5000º F.
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Tungsten, as it burns long and brightly.
That type of bulb makes its light by making a small piece of tungsten wire glow at around 3000 degrees Celsius. Obviously that process also produces a lot of heat so incan…descent bulbs are inefficient, i.e. they produce not much light for a lot of electric power used. Tungsten is used because it has the highest melting-point of all metals.