Bulb Definition and 285 Threads

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?

Does anyone know what it is, or where I can find the surface area of a typical 60W incandescent bulb filament? (if possible, by GE) I'm working on a research project and we're applying the stefan-boltzmann law. I'm calculating an area around 3e-5 m^2. I figure I'm in the ballpark, but I'd...

My son is working on his science fair project. I had told him that LED bulbs produce voltage in sunlight and he's been exploring that and is trying to see if he can charge a cell phone using LED bulbs under a light source. Using dozens of small LEDs, he is producing about 5v under a light...

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.

Which bulb is really more collisions of electrons inparallel connection? Maybe we can easily get the conclusion about this question. The intensity of bulb's light is depend on the power of electricity(IV), so the upper blub has more number of collisons between electrons and atoms. but I...

Suppose I have 10.2 W power source... Now how many 1 W bulb can I use here? Obviously I can use 10 bulbs at their best here... But can I use an eleventh one? Usually we do it like this 10.2/1=10.2~10 but my ques is there is some power left here... So why can't we use one more? This will...

We know that the intensity of the light in the light bulb depends on the electric current. And I want to know who was the first physicist who proved this. And if there is a possibility could you also tell me how, why, when, where he did this experiment or give me an website, but the name of...

I recently changed my bulbs in my car's HVAC dash to LEDs. I wanted a blue color and it looks really good and exactly what I wanted. The only problem is that there are three buttons that are lit separately from the new LEDs by green bulbs, which I want to be blue as well, but I cannot simply...

Homework Statement A light bulb is rated at 30 w when operated at 120 v. How much charge enters (and leaves) the light bulb in 4.0 min? ans is 17 C Homework Equations I = P/V i = dq/dt The Attempt at a Solution I = P/V = 30/120 = 0.25A q = I*t = (0.25)(4*60) = 60 C...

why an bulb blinks during low voltage?

I know that incandescent bulbs are filled with some inert gas to reduce the rate at which the filament decays. If the filament was to be exposed to ambient air, how long before it evaporated? How long can a mesh of light bulb filaments (or other material with as high a melting point that can be...

Hi, I am trying to build a conductivity meter as part of a school project (I have to measure the conductivity, among other things, of local water systems). Unfortunately, I cannot buy one for this project, as it should be home-made for these purposes. If I wanted to create a meter that...

1. A 25 ohm resistor is connected in series with a 100 W light bulb. The standard 120V/60Hz AC outlet voltage is applied to the series combination. Determine the real power dissipated on the light bulb. Assume the internal resistance of the light bulb is independent of the power dissipation...

In a battery-powered light bulb, what is happening in the light bulb that makes it light up? To understand what I mean by a battery-powered bulb, visit this link: http://science.howstuffworks.com/innovation/everyday-innovations/how-to-make-battery-powered-light-bulb.htm Thanks!

I was cleaning up my lab and I came across some quipment I've never seen before. The top looks like a thistle tube, but there is a closed bulb on the bottom. Furthermore, there is another glass piece inside of the stem. The piece inside of the stem is sealed on the top. It has an open at...

Homework Statement There are 100 light bulbs in a box. 20 are 40 watt, the rest are 60 watt. If we randomly choose 10 bulbs, what is the probability that there will be exactly 2 40-watt bulbs? What is the probability that in a random sample of 10 bulbs there will be at least 1...

Homework Statement See attachment The question asks to calculate the brightness of the bulbs(g and h) in this new configuration. Homework Equations Since brightness \propto Power P= V^{2}/R P= I^{2}R E.M.F of One cell : V The Attempt at a Solution I used the equation P...

I have been scanning a physics book. See attachment. The diagram shows that a light bulb has a continuous spectrum while the hydrogen has discrete spectral lines. Since the filament in the bulb is tungsten, why doesn't the light bulb also have discrete spectral lines?

Homework Statement What is the apparent magnitude of a 100W light bulb at a distance of 3 m? [Hint: Compare with the Sun to eliminate the unknown constant in the expression relating flux density to apparent magnitude.] . The solar luminosity is L \approx 4 \times 10^{26} W. . The Earth-Sun...

Homework Statement There was this question involving a pendulum expriment: the five values of the square of the period (T^2) was plotted against the 5 values of the distance y in centimetre from the floor to the centre of the bob. I was then asked to determine the intercept on the...

Homework Statement Homework Equations The Attempt at a Solution First I originally tried using kichhoff's rules, but didn't get far. What is throwing me off is they are giving me the current of the battery instead of the voltage. Since I know circuits in parallels all have...

I have included a diagram of this simple circuit I have constructed. When hooked up to the battery, the motor starts out slow, and then speeds up to a ~constant speed. The bulb, however, starts out bright but immediately gets dimmer, almost to the point of no light being produced. If...

Hi This might seem odd but I need to explain my friend on this Friend and I agreed that Classical physics is time reversible (i.e. laws remain same if time is reversed.. e.g. gravitational pull on a projectile.) only exception is II law of Thermodynamics (which talks of irreversible decrease...

Homework Statement Problem is give in the image Homework Equations V=IR The Attempt at a Solution Since its a series circuit i tried that current should be the same so it's 9/20 since there is no resistance in the bulb which is 0.45 Ω somehow the answer is 0.3Ω. why is that the...

So I just saw this joke and I thought y'all might get a kick out of it (at least those who have read one of the bourbaki books) Q: How many Bourbakists does it take to replace a lightbulb? A: Changing a lightbulb is a special case of a more general theorem concerning the maintain and repair...

Hello. I just got a PMT the glass bulb of which has been broken. Even if performances are not the best, do you think I can use it as an Electron Multiplier (with all convenient electronics) ?

Homework Statement figure 1 shows the relation ship between voltage and current when voltage is applied o a certan light bulb. Next as shown in figure 2, the bulb os connected n series with a 12V battery and 5Ω resitor. Figure 1 http://imageshack.us/photo/my-images/585/imagnecir.png/...

Homework Statement I'm studying for my GCSE exam and I need to know how changing the voltage across a bulb affect it's power output for my secondary evidence, i have searched the internet for the answer but can't find anything. Anyone know how it affects it OR any useful websites to use...

Homework Statement 20 bulbs are wired together in a series position. A) what happens if 10 more bulbs are added in series? B) the bulb was modified such that an additional resistor is placed across the filament (parallel to the filament). The value of the resistor R is much larger than the...

A DC circuit has resistances of 10Ω, 12Ω, and 10Ω respectively. Also has 2 light bulbs with identical tungsten (resistivity = 5.6* 10^-8) filament bulbs with filament thickness of 12um and length of 1.2cm. The source is a 12V. what is the power loss over the first light bulb? I am not...

Hey, I have a question regarding practical electricity. Since we know that power (rate of energy released) determines brightness of bulb, then: Since P = VI and V = RI, it implies 1. P =(V^2) / R 2. P = (I^2) * R How can we tell if power increases or decreases when resistance (R) of...

So I have a hilarious idea waiting to be exploded onto the world and I need a green light bulb. I have this bulb that is a 2.5V 0.3A incandescent bulb. I'm not entirely sure I know how to determine the type of base, but I could probably grab a micrometer and some diagrams and figure it out...

I'm wiring a 25W Edison bulb to an old GE clock/radio. The radio is 120V/60hz 8.5W input. Basic calculation I = P/E would mean the current is 0.07A If I wire the bulb in parallel between source and the clock/radio, there's now 0.2A for the bulb branch and 0.07A for the clock/radio...

Hi all, I have a doubt which I would like to hear your opinion and answers about. So, I was comparing different light sources for my research, and I started thinking about a sentence which I've always taken for granted: incandescent light bulbs waste more than 90% of their power as heat...

Hello, this is my first post. I googled it, and searched the forums, but no luck. I want to know what I need to build a device, that can light a small light bulb. Something rather small, such as a flashlight bulb. But I need the on/off switch to be a photocell that is sensitive enough to make...

Whoosh! Just read electricity. Resistance results in heat. The filament of bulb uses heat to light up. Keeping this in mind and the equations of power, current, voltage, resistance: °Light bulb uses current or resistance to light up and illuminate? °What's the difference between a...

Does anyone think that it's possible to have a perpetual motion machine electricity generation of a combo of a light bulb shining light on photovoltaic cells that are connected to power increase transformer coils to power that light bulb? I suppose there would have to be some kind of way to...

Homework Statement When a single round bulb of a particular kind and two batteries are connected in series, 5* 10^18 electrons pass through the bulb every second. When a single long bulb of a particular kind and two batteries are connected in series, only 2.5*10^18 electrons pass through the...

How many watts should a 40w bulb use at 120v?

In my physics lab, I calculated a value of 5436 deg C for the max temperature of the filament by measuring its resistance. Is it possible for a filament to reach this temperature? I'm thinking it might be since the wire is so small that it wouldn't kill the world.

1. Homework Statement Estimate the radiation pressure due to a 100 W bulb at a distance of 8.4 cm from the center of the bulb. 2. Relevant equations Power= Work/Time W=Force(distance) Pressure = Force/Area = Poynting vector/speed of light 3. The Attempt at a Solution I found the cross...

I was given an amaryllis bulb in early December. It came in a box with a large peat pellet, a pot, and the bulb. I planted it, and it started to grow. It's got one flower stalk, and some leaves, but recently the leaves have flopped over and are turning yellow at the base. I think it's...

Photons activate hormones in us which cause us to wake up. I'm wondering if there is a different between the photons coming from the sun and the photons coming from a light bulb? Do these both have the same effect on the body? I've put this in the classical category because of optics.

On Light bulb appliances there is often a 60w limit. I would guess that a halogen bulb of 70w would produce less heat so should be fine to put in similar fittings.

In the picture below http://www.geo.mtu.edu/rs/back/spectrum/e_mag.gif a bulb is placed on a wire parallel to the direction of the electric field. The bulb is directly on the x-axis where the two waves cross each other. 1. Would the bulb glow when the wire is parallel to the direction...

Homework Statement A light bulb and a resistor are connected in series to a variable power supply. A student first connects a voltmeter and an ammeter to measure the current through and the voltage across the bulb, as shown in the left circuit. The student varies the power supply voltage and...

hi member! i would like to have your ideas on how to program my microcontroler to input a specific value to the light bulb so as the brightness to be as specific as i require, if any fore circuit is also required,i'm here to accept and utilise ideas

why do we call a zero watts bulb as it so?? a zero watts bulb is common in houses,commonly called as 'night lamp'.., if v say it as zero watts lamp., then is it conducts zero current or zero voltage? what is the power consumption by modern led lamps and by other fluorescent lamps??

Greetings! This is my first thread. I am creating a 200V bulb dimmer using PWM and IGBT. Currently, this is how I connect the components: The output of the PWM goes into the gate of IGBT. The bulb connects in series with the 220V supply and the collector of IGBT. The emitter of IGBT is...

Two 40-watt bulbs are connected in parallel to a 120-volt circuit. What is the current in each bulb? Choose one answer. a. 1/4 A b. 1/3 A c. 1/2 A d. 2 A e. 3 A I used V = IR and P = V^2/R My attempt 40 W = 120V^2 / R giving R = 360 1/R + 1/R = 1/Req => 1/360 + 1/360 = 1/Req =>...