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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.

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โˆ™ 2008-08-06 20:53:01
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Q: How hot does a filament light bulb get?
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Related Questions

What Part of the bulb gets hot and produces light?

The part of an incandescent light bulb that gets hot and produces the light is called the filament.


Which type of light bulb glows when a filament inside it gets hot?

An incandescent bulb.


How hot does a incandescent light bulb get?

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.


Is a light bulb a kind of lever?

No. A light bulb is a bulb that contains a filament that gets hot when electric current is passed through it.


What is the part of a light bulb that gets hot and produces lights?

In an incandescent light bulb this is the filament. It is usually made of tungsten.


What does the support wires do on a light bulb?

As the name implies, support wires support the filament wire in the bulb, The filament, of course is the wire that glows white hot, giving out light


What type of light is a light bulb that uses a filament?

A light bulb that uses a filament is also known as an incandescent light bulb.


What are the uses of a filament light bulb?

The filament is the one that throws off light in the bulb.


Why does a light bulb filament glow?

The filament inside is heated. Once it gets hot enough, it dissipates some of the energy as heat and light.


How is light produced in an incandescent light bulb?

An incandescent light bulb has a coil of tungsten wire (called the filament) suspended in an evacuated (of air) glass bulb. Electricity is passed across the filament which, because of its resistance glows white hot, producing the light. The filament does not melt or burn away because the melting point of tungsten is high and there is not air in the glass bulb for the hot tungsten to react with.


Is a light bulb filament as hot as lava?

The filament of an incandescent light bulb is actually significantly hotter than lava. Temperatures may exceed 4,000 degrees in some bulbs.


Why do you need to have the glass on the outside of a light bulb?

The glass envelope, or bulb, of an incandescent light bulb is needed to hold the inert gas, such as argon, that fills the space. The filament of a light bulb is made of tungsten wire. When electricity passes through it the filament becomes extremely hot and emits light. The inert gas surrounding the filament protects it from evaporating too quickly. A light bulb only lasts as long as its filament lasts.


What is the filament of a light bulb made out of?

The filament of a light bulb made out of an element known as tungsten.


How does electricity light a light bulb?

The incandescent light bulb has a filament of Tungsten inside it. When electricity flows through the bulb, it heats up the filament. This causes the filament to glow and emit light.


Does the filament of an incandescent light bulb glow because it gets extremely hot?

yes


How is resistance used to create light in a tungsten light bulb?

Electricity creates heat when flowing through a resistor such as the filament in a tungsten light bulb, and, since the heat can not be readily conducted away in the near vacuum inside a light bulb, the heat eventually raises the temperature of the filament to a value that leads to radiation of light from the hot filament.


How does an electric circuit light up a light bulb?

The element (filament) in the bulb passes electricity but has a certain resistance - pushback. It's this pushback that makes the filament grow hot with the current flowing through it from the circuit and when the filament is hot enough it produces light. The electric circuit is there to prove the current flow which heats the element and produces light.


What is a filament Is it solved by using electricity terms?

A filament is part of a bulb.I will give you a full sentence. "The filament of a bulb is the part that gets hot and produces light"


Why a bulb with a filament gives off light?

Electricity goes through the filament in the bulb.The filament is made of a material that is not a good conductor and therefore offers "resistance" to the electricity going through it.The "resistance" results in the filament is a form of friction to the electric current.The electrical friction results in the wire getting warm, then hot, then very hot.The filament gets so hot that it starts to glow, giving off light.


Why bulb glows when current flows through it?

The filament in the bulb has resistance. The current flowing through the resistance of bulb causes the filament to dissipate energy in the form of heat and light. The filament is actually glowing white-hot because of the energy it is dissipating, thus giving off light.


Why do light bulbs burn out?

Light Bulb Filament Life Story Incandescent light bulbs have a filament made of tungsten. The filament is heated to a white-hot temperature by the electrical current passing through it. The filament is so hot that the tungsten slowly evaporates off the filament and plates the inside of the glass envelope (bulb). The evaporation of metal causes the filament to get thinner over time. Repeated heating and cooling from turning the lamp on and off causes the filament to become brittle. A large surge current flows through a cold filament when the bulb is first turned on (the resistance of tungsten increases with temperature reducing the current as the bulb heats.) The surge passing through a brittle, thin filament can create a hot spot that completely melts the filament causing the light to burn out. This is why light bulbs tend to burn out when being turned on.


What does a light bulb have to do with an electrical light source?

A light bulb is a source of electric light. In an incandescent light bulb, the glass bulb forms a protective shield around a glowing filament. The air inside the glass bulb is removed, or replaced with an inert gas. Electric current is passed through a thin metal filament (usually tungsten), which causes it to glow white hot, giving out light. The protective bulb stops the filament from burning up, as it has no Oxygen.


What is the function of the Tungsten filament in a light bulb?

This incandescent filament emit light.


What does the filament of a light bulb allows the light bulb to change electrical energy to?

The filament of a light bulb overs enough resistance to current flow, that the filament heats up so much that it will glow and produce visible light.


How does the resistance of a light bulb filament change after the light has been turned on?

The electrical resistance of a light bulb increases when it is turned on As a resistor, the tungsten light bulb has a positive resistance coefficient. This means that the electrical resistance goes up when the filament becomes hot. For example, a 100 watt light bulb operated at 120 volts - it does not matter if it is AC or DC for this calculation - will have a resistance of 144 ohms when hot and draw .833 ampere. When cold the filament typically has a resistance of only 10 ohms which increases as the filament heats up.