What is Light bulb: Definition and 142 Discussions

An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated until it glows. The filament is enclosed in a glass bulb with a vacuum or inert gas to protect the filament from oxidation. Current is supplied to the filament by terminals or wires embedded in the glass. A bulb socket provides mechanical support and electrical connections.
Incandescent bulbs are manufactured in a wide range of sizes, light output, and voltage ratings, from 1.5 volts to about 300 volts. They require no external regulating equipment, have low manufacturing costs, and work equally well on either alternating current or direct current. As a result, the incandescent bulb became widely used in household and commercial lighting, for portable lighting such as table lamps, car headlamps, and flashlights, and for decorative and advertising lighting.
Incandescent bulbs are much less efficient than other types of electric lighting, converting less than 5% of the energy they use into visible light. The remaining energy is lost as heat. The luminous efficacy of a typical incandescent bulb for 120 V operation is 16 lumens per watt, compared with 60 lm/W for a compact fluorescent bulb or 150 lm/W for some white LED lamps.Some applications use the heat generated by the filament. Heat lamps are made for uses such as incubators, lava lamps, and the Easy-Bake Oven toy. Quartz tube halogen infrared heaters are used for industrial processes such as paint curing or for space heating.
Incandescent bulbs typically have short lifetimes compared with other types of lighting; around 1,000 hours for home light bulbs versus typically 10,000 hours for compact fluorescents and 20,000–30,000 hours for lighting LEDs. Incandescent bulbs can be replaced by fluorescent lamps, high-intensity discharge lamps, and light-emitting diode lamps (LED). Some areas have implemented phasing out the use of incandescent light bulbs to reduce energy consumption.

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  1. C

    Finding gauge pressure for gas inside light bulb as it heats up

    For this 19(a), The answer is 0.137 atm. My working is ##P_{gauge} = P_f - P_i## ##P_{gauge} = \frac{nRT_f}{V_f} - \frac{nRT_i}{V_i}## ##P_{gauge} = \frac{nRT_f}{V} - \frac{nRT_i}{V}## since volume does not change ##P_{gauge} = \frac{nR}{V}(T_f - T_i)## However, I am not sure how to go from...
  2. O

    Misc. Let's change another light bulb

    You've helped me change a couple bulbs so far, hopefully this is the last one. There's a recessed light on a hinge (a gimbal light maybe?) There are three exterior white rings - the outermost is a trim, the middle is a flat piece, the inner is ridged. Both the middle and inner piece move on...
  3. J

    I Minimum light bulb wattage for solar simulator

    I am trying to design a simple homemade PV solar simulator. I have picked metal-halide lamps as my light source. If the PV panel has an area of 1m^2 and I wanted to achieve spatial uniformity across the irradiated surface with an irradiance of 1000 W/m^2, how do I go about selecting what...
  4. Dario56

    I Energy Flow From Battery to the Light Bulb

    When we connect tungsten filament light bulb to the battery, filament becomes hot due to electrons losing kinetic energy in the electric field inside of conductor. Heat is eventually converted to electromagnetic radiation making light bulb shine. Light energy comes from flow of electrons and...
  5. O

    Misc. How do I change a really high light bulb?

    Your guys really helped me out with my last bulb problem so I thought I'd try again. There's a bulb over a staircase that is - a recessed floodlight - about 18 feet above the stairs directly beneath it (it's over the bottom of the stairs, and the staircase is exposed to the next floor) About...
  6. M

    Can a Resistor Simulate a Light Bulb Load for LED Bulb Installation?

    Hello All, I have a snowmobile that uses a shunt type regulator to control voltage. They require a constant load (headlights) to work proper. The 2 stock bulbs are 55 watts on low with the system running 12v. Racers install another set of hand warmers, wired to high, and tape them to the...
  7. T

    Why doesn't a light bulb draw 100 amps?

    I am asking this question in behalf of my father ( who does not have an account here to ask this question himself). My father said he does not understand why a simple light bulb in an AC circuit does not draw far more amps than a simple light bulb draws. He thinks that a typical light bulb...
  8. S

    Is it possible to build a laser from a light bulb?

    In my drawing you can see: A generic bulb covered by a mirrored hollow ball. The hollow ball has a small hole (1 mm diameter). So the complete light will go through this small hole. The lens will bundle the light in a very distant (100 km) focal point. I guess it might be hard to create such a...
  9. Greg Bernhardt

    Anyone have a light bulb blow up?

    Was shaving just now and one of my mirror wall light bulbs blew up. Luckily it's encased in the light fixture with an opening at the top so it was contained a bit, but some glass blew up through the top and rained on me. The glass was very hot, so I'm guess it wasn't LED.
  10. H

    How to find the power consumed by the light bulb

    Homework Statement (Is the image read-able now? ) The fig 1 shows the relationship between voltage and current when voltage is applied to a certain light bulb. Next, in fig 2, the bulb is connected in series with a 12-V battery and a 5 ohm resistor. Question : what is the amount of power...
  11. zdcyclops

    B If the moon were a light bulb how many watts would it be.

    If the moon were a light bulb how many watts would it be.
  12. M

    Light Bulb in a Box: Velocity Change After Release of Photon?

    Homework Statement [/B] A box is traveling with a certain velocity in space. Inside the box is a light bulb, which is capable of releasing one photon of light. The light bulb harnesses the energy from the box; it does not require an outside power source but instead uses the energy on the...
  13. C

    Electric circuits -- Finding the V-I characteristics of a light bulb

    Homework Statement Homework EquationsThe Attempt at a Solution I know Ammeter and bulb goes in series and Voltmeters in parallel. But am I supposed to connect the voltmeter to the little arrow on the potential divider, or just across the bulb?
  14. N

    Bulbs that only emit long IR (>1200nm) or 1000K color temp.

    I am looking for bulbs that would be emitting a spectrum characterized by a color temperature of between 500K and 1000K or any kind of light fixture that only emits long IR wavelengths. Does such a thing exist?
  15. dholbach

    Can a cathode ray tube be made from a light bulb?

    Light bulbs and cathode ray tubes are structurally similar in some respects. For example, both contain a filament -- in the light bulb, the filament heats up to produce light, while in a cathode ray tube, the filament emits electrons, which are then steered into a target (in a CRT TV, the...
  16. N

    Checking the voltage in a light bulb socket

    Hello, I was trying to check with a voltage tester if there was voltage in a light bulb socket (Edison type, no bulb present). Explosion happened (a relatively loud sound) and the safety circuit switch turned off. My question is, how can one explain this with the laws of physics and how can...
  17. V

    Uncovering the Source of Extra 267 J in Standard Incandescent Light Bulb

    Ok, according to my in depth research, wiki, the filament of standard incandescent light bulb will reach a temperature of roughly 2500 K. According to Stefan-Boltzmann, the power radiated from an object at temperature T (K) is given by P= A ε σ T^4 . Suppose the filament has a radius of 1mm...
  18. Alvaro8

    Help with light bulb radiation

    Hi guys I´m doing an experiment in thermocouples electricity generation by thermal radiation of Sun (As an addition to Solar panels). I´m still in high school and I don´t know a lot about the topic. I would like to simulate sun thermal radiation with a 100w incandescent light bulb as an...
  19. A

    Removing a Light Bulb: How Does it Affect Resistance and Current in a Circuit?

    Homework Statement Homework Equations Ohm's Law, Equations for parallel and series combinations of resistors[/B] The Attempt at a Solution Working this problem I obtain a solution that doesn't make sense, which is that the bulbs are dimmer. If I assign 10 ohms to each bulb, I believe...
  20. Zero-shift

    MIT graduates cannot power a light bulb with a battery

    Now, to be honest, I can comfortably light it with TWO piece of wires and not ONE. So , was it a trick question? Technically, those are havard grads. Please weigh in.
  21. kamhogo

    Light bulb & Diode: linear or non-linear elements.

    Homework Statement These questions are related to an experiment where we had to record the current for varying values of potential difference (10 readings), then repeat the process with the applied potential difference was reversed a) Why is the resistance of a light bulb not constant? b) Does...
  22. T

    B A question of timing in a light bulb

    Is there any physical law that prevents the electrons in the filament of a light bulb from emitting light? How come we always see light? What are the probabilities that all the electrons in the filament fail to emit light at the same time? I suppose there is a conservation law somewhere...
  23. F

    Can MRI Detect a Light Bulb Inside a Closed Box?

    I put a light bulb inside a box and make it glow, is there a way to know where the light bulb is if the box is closed and not transparent
  24. TheAxolotl

    How is the vacuum in a light bulb sealed?

    I understand that one would use a vacuum pump to evacuate a light bulb, but once a vacuum is created, how is the bulb sealed without air coming in?
  25. P

    Light bulb in a microvawe oven

    I'm sorry to reopen the debate on what happens when I put a light bulb in a microvawe oven, but the question is driving me crazy. I'm debating with other students about "why I light bulb lights up when I put it in a microwave oven ?". I read the old thread posted in 2003...
  26. A

    Light Bulb and Transmitted Intensity?

    Homework Statement You have a light bulb where the filament (in vacuum space) starts to glow. This light hits the glass of the bulb at 90 degrees from distance R and is transmitted through the glass of thickness s into the air, of index of refraction nair. So light travels like this: vacuum...
  27. M

    Halogen light bulb filament thicknesses?

    Hello, new to the forum, just a average guy, not too much more informed on physics then the average person, so this will be a pretty simple question, anyway, to my question: with halogen bulbs, does higher wattage always mean thicker filament? Because i am trying to work out if tricky Chinese...
  28. J

    Help with removing a light bulb from motorcycle circuit?

    Hello there. I was looking for a place on the web where someone with an electrical understanding might be able to help me. I have a gas powered scooter which I wanted to make a change to the lighting circuit. My question is regarding the resistor in the circuit. With this circuit, while the...
  29. F

    Kirchoff's Law - Wire in parallel with light bulb

    Homework Statement If you measure the resistance of the three lightbulbs (independently) and get the following values. What is the equivalent total resistance of the circuit, and it’s uncertainty. R_1 = (50 \pm 7) \Omega, \ \ R_2 = (720 \pm 30) \Omega, \ \ R_3 = 140 \pm 20) \Omega Now you...
  30. Kostas Tzim

    Mysterious Phenomenon: Magnet & Light Bulb

    Guys i noticed something i can't explain, i was playing with a magnet while i was studying and my hand, where the magnet was, remained near the light bulb for some seconds, soon enough i realized that a strange sound was emitting then when i moved away my hand the emission stopped. What's the...
  31. Z

    Create DIY Light Intensifier Using Disposable Materials

    1. I am supposed to create a device that can intensify the light directed at a light intensity sensor. A small light bulb will be 25 cm away from the light sensor. My device is required to be 20cm long and placed in between the light bulb and the light sensor in order to make the light that is...
  32. NoSniping

    E&M: AC Circuit Light Bulb

    Homework Statement How large an inductance should be connected in series with a 120 volt (rms), 60 watt light bulb if it is to operate normally when the combination is connected across a 240 volt, 60 Hz line? (First determine the inductive reactance required. You may neglect the resistance of...
  33. atyy

    Graphene Light Bulb: Advantages & Tech Breakthrough

    http://www.bbc.com/news/technology-32101473 The BBC reports that a graphene light bulb will go on sale. What are its advantages over current technologies?
  34. S

    Apparent Depth of Light Bulb above Water and Mirror

    Homework Statement Hey, so there is a light bulb above a tank of water which has a mirror at the bottom. I am trying to find the apparent depth of the image of the light produced by the mirror. Finding the apparent depth of the mirror is easy, but I am confused on what to consider the object...
  35. I

    Light Bulb Illumination: Understanding the Role of Current and Energy Transfer

    I am having some trouble with discerning whether current (electrons flowing through the Tungsten), or the energy transfer as described by the poynting vector, is responsible for lighting the lightbulb.
  36. P

    Lightbulb brightness in a circuit

    Homework Statement The circuit has identical light bulbs. A fourth identical light bulb is added to the circuit. How does the brightness of the original light bulbs change? a)All of them get dimmer b)X,Z get dimmer, Y brighter c)X,Z brighter, Y dimmer d)X,Y dimmer, Z brighter e)X,Y brighter, Z...
  37. N

    Does a CFL Pose a Fire Risk Due to Inductive Load Characteristics?

    As far as I know, Compact Fluorescent Lamp (CFL) is an inductive load. I understand that inductive load doesn't allow an immediate change in current. When the circuit was initially open (through open switch) then became close, the inductive load was energized. So opening again the circuit after...
  38. dragoneyes001

    Light Bulb Moving at Half the Speed of Light: Effects on Light Halo and Length

    quick question when a light source is moving at a good clip like the above where the light bulb is moving at half the speed of light am I wrong in the drawing that the light halo would be lagging towards the back but even on the two sides? what I'm wondering is how long would the light behind...
  39. Celestion

    Optimum mounting angle for three LEDs in a 240V LED light bulb

    Homework Statement The asker needs to know the angles to mount three LEDs inside a traditional mains powered light bulb shaped enclosure "to get even radiation from the LEDs", and also the position of the covering plastic sphere in relation to the LEDs. (I was thinking that the position of the...
  40. Heros

    Uncovering the Mystery of Non-Linear Torque in Muscle-Powered Energy Conversion

    Hi, i didnt know where to put this question cos its kind of multitopic, here is why... I am working on a better way to take mechanical energy from muscles, i made a teste bench for pedalling in very different ways, including traditional(circular) pedalling, the thing is. I am measuring the power...
  41. S

    Triac - Power dissipated in light bulb

    Homework Statement A triac is used in a dimmer switch to control a 100W light bulb. If the firing angle is set for α=∏/3 estimate the power dissipated in the bulb Rated at 100W and the voltage source 230V @ 50Hz. Homework Equations Vpeak = Vrms/0.707 The Attempt at a Solution...
  42. gfd43tg

    Filament radiation in light bulb

    Homework Statement A light bulb has an internal filament with a total surface area of 2.5 X 10-3 ft2 that operates at a temperature of 2240 F. The filament has an emissivity of 1.0 and radiates through a vacuum to the glass wall of the bulb. Only 10 percent of the total energy emitted as...
  43. T

    Find the power of the light bulb

    Homework Statement In the figure below, you will attach one or more light bulbs of R=30.12 Ω in parallel with the battery (with ε = 20 V, internal resistance r). (i will upload with work and the picture of the wiring diagram) a.) For an ideal battery (r=0), what would be power...
  44. B

    Measuring Power Consumption of a Light Bulb with a Dimmer Switch

    Hi guys, For a science experiment I've got to measure the power consumption of my circuit of a 100W incandescent light bulb connected to the mains AC, with a dimmer switch to vary its brightness. I was planning on just using one of those plug-in energy monitors with a digital display but...
  45. M

    Mass of Light Bulb Change From Adding Ideal Gas

    If you have a light bulb that weighs 10 g when empty, how does adding an ideal gas inside of it change the mass? If I'm not mistaken, the force the gas exerts on the light bulb (well, a perfectly symmetrical object is a better example) is the pressure, and it would be pointing in all...
  46. E

    Regarding modeling of light bulb circuit

    Hello, I'm trying to apply conservation of energy to a lightbulb circuit, but I can't think of what term should be included for heat loss / convection / conduction Here's what I've got Pin = Pradiated + i2Rwire, connections, etc + Power lost to heating surroundings? (what can I use for...
  47. D

    Find light bulb surface temp from temperature measurements

    Homework Statement I have 3 data points of steady state temperature at 3 locations some distance away from a bulb, I need to calculate the temperature of the surface of the bulb. It would be best to assume the bulb is a hemispherical radiation source, based on the experiment set-up...
  48. B

    What produces the photons in light bulb filament?

    What produces the photons in light bulb filament? I know that electrons are emmitted by thermionic emmission from the filament . . . do they then fall back into the filament and emit EM radiation as they de-accellerate into the filament?
  49. I

    Plasma inside a light bulb?

    http://i.imgur.com/bLUjP0Q.jpg is something like this even possible in a light bulb? i thought the interior was supposed to be a vacuum.