Bulb Definition and 282 Threads

A light bulb is completely covered with a thin coat of black soot in a room maintained at 20 degree celsius. If the shell has an equilibrium temperature of 100 degree celsius. What is the wattage of the bulb? I can't understand how to do it. I am a student of 9th standard.

Dumb question, I know. But what exactly does it mean? Does it mean 36watts is what a bulb will consume at 12v?.. And does '12v' mean that the bulb will only work at 12v. What if you connect the bulb to a 24v supply? Please excuse my ignorance.

Hi, I am stuck on this question, any help would be appreciated. Thanks! The tungsten filament of a certain 100 W light bulb radiates 2.85 W of light. (The other 97.15 is carried away by convection and conduction) The filament has surface area of 0.400 mm^2 and an emissivity of 0.952. Find...

Hi guys.. Would a light bulb's current and voltage change according to ohm's law? Thanks..

hi, wish to ask, if experiment like below image : http://img168.imageshack.us/img168/4417/image28ei.png would the bulb lights for a "moment or X milisecond?" once we touch the wire B to the bulb? assume the wire B is a long long wire (just wire) wire A already attached to positive...

HOLY S*** my CF bulb burnt out! LITERALLY! OK UHMMMMMMMMMMMMMMMMMM My CF bulb... that's probably been in use for a year or 2... just burnt out... LITERALLY! It faded in and out and then it became really dim and a bit orange inside and then it became even mooooore dimmer and then it flat out...

http://img224.imageshack.us/img224/5535/physics31id.png "Light bulbs with the wattage ratings shown in the figure above are connected in a circuit. (a) What current does the voltage source deliver to the circuit? (b) Find the power dissipated by each bulb. (Asusume normal operating resistances...

I have a great invention! It's great for many reasons! 1. I thought of it 2. People are lazy and will use it 3. Guys exist 4. Women are annoying 5. I thought of it What's the most annoying thing that one has to do in their life? The most mind-numbing, boring, stupid thing one will ever...

An incandescent bulb has a resistance of 12 *omega when it is at room temperature (25 degrees C) and 400 omega * when it is hot and delivering light to the room. The temperature coefficient of re- sistivity of the filament is 0.008 (degrees C)^-1, where the base resistance R0 is determined...

Why does an electric light bulb nearly always burns out just as you turn on the light, but almost never while the light is shining? :confused:

Well the question asked us to make a rough estimate of the temperature of the filament in an ordinary electric light bulb which emits white light. And if it has radiated power of 100 W, make a rough estimate of the surface area of filament. Well, the thing is how u make a rough estimation on...

Given two light bulbs with the following ratings: 75.0W 120VAC and 100W 120VAC. They are connected in series across a potential difference of 120. VAC. Assuming that the operating resistances of the bulbs are not affectd by the series connection, calculate (a) the power produced in each bulb...

You have a light bulb in the middle of a room and ... Hi people, here's an easy question for you. I was asked this by a guy down the pub a few days ago, I think I know the answer, but they don't believe me. If you have a light bulb switched on in the middle of a room and then you put mirrors...

I'm not sure I'm doing this correctly... If all of the energy from a 60-watt bulb was put into 1 gram of water at room temperature for 2 seconds, how much would the temperature of the water increase? I tried it using the example but I wanted to check my answer first. 60 * 2 = 120 120...

:confused: ??

When bulb light passes through a prism why doesn't it give different colors? From what I understood about light bulbs, it should give red, orange and yellow as descrete lines. Why doesn't this happens and it goes out of the prism almost as it enters? Thanks

I did a physics lab about diffraction grating where we had to determine the angular positions of all spectral lines of the helium discharge tube. I have 3 questions : 1. Why use a discharge tube instead of a light bulb? - I think it might be because you would have to break up the white...

Hey guys I am having some trouble with this simple questions: What is the resistance of a light bulb that uses an average power of 75.0 W when connected to a 60.0 Hz power source having a maximum voltage of 190 V? (b) What is the resistance of a 120 W bulb? I tried doing it by...

Which of the bulbs shown in the figure will light up first when the switch is closed? E: cell K: key A,B,C: bulbs PS: If it tells you that you don't have permission, logout and then login again to see it.

Gday, This is a very simple question and it should only take one sentence to answer. It's not worthy of these forums, lol, but despite my efforts I cannot find an answer through google. If a light fitting says '40 watt max' and I stick a 60 watt bulb in it, will that have any adverse...

http://ca.pg.photos.yahoo.com/ph/sikandar1984/detail?.dir=9181&.dnm=8e2e.jpg&.src=ph This link is a diagram for this question It says the cross section of a parabolic reflector of a headlight is shown in the diagram. Determine where the bulb should be located if it is positioned at the...

Hi all. I'm wondering how people determine the lifetime of a light bulb. Do they really turn on the bulb and wait till it go down? Or there are special methods to shorten the duration of the testing experiment? Anyone know?

True or false? Answer: http://www.snopes.com/science/lightbulb.asp

We have two bulbs, X and Y. Y has thinner and longer filament than X. When connected to a power supply which bulb will give out most light and why? I think the answer should be Y as it has heigher resistance and therefore will dissipate more energy. Thanks in advance. :approve:

You are in a room with 3 light switches. These switches are connected to 3 separate light bulbs in an ajoining room. Access to the ajoining room is via a door that remains closed, there are no windows, other people etc etc. You are allowed to enter the ajoining room once and then return. At...

Q: How can the prisoners tell, with certainty, that all 100 of them have visited the central living room with the light bulb. The riddle: 100 prisoners are in solitary cells, unable to see, speak or communicate in any way from those solitary cells with each other. There's a central living...

Q: How many forum members does it takes to change a light bulb? A: * 1 to change the light bulb and to post that the light bulb has been changed * 14 to share similar experiences of changing light bulbs and how the light bulb could have been changed differently * 7 to caution about...

as part of a physics practical write up i have to measure the temperature of a light bulb envelopes temperature as the voltage increases. first ... am i right in thinking a type J exposed thermocouple would do the trick for this? if so, i heard something about one end being cold, to...

Hi all, I have two light bulbs, both for 230 volts. One has 100 watts, the other 15 watts. It is clear that the 15W bulb has the higher resistivity. But is its filament a) longer b) thinner c) both, and why? Thanks!

How may watts does a 60-watt light bulb use in three hours? 60*3=180watts?

hi guys i want know how many watts does a lighting have? --------------------------------------------------------- (lighting=the power that exchange between clouds an earth) (im sorry about my english words becaus i don't speak english) thanks bye

I had to do some homeowrk problems and i was hoping someone could just double check my answers... much appreciated. When you connect a 120 watt bulb and a 60 watt bulb in a parallel circcuit across a standard 120 volt outlet, which is brighter? the 120 watt bulb is brighter- right? because...