Bulb Definition and 285 Threads

Where is the best location for a light bulb filament to be placed in a spotlight, when using a concave mirror? It makes the most sense to put it at the focal point of the mirror if you want parallel light beams but are you supposed to have parallel light beams when you use a spotlight? Or do...

If the 'average' intensity of direct sunlight on a warm summer day could be re-produced in a full spectrum light bulb, how many watts would that bulb be? I'm trying to find a bulb I can use to calibrate a photo sensor to sunlight intensity but my shop is on the base floor where there are no...

Homework Statement Hook up a round bulb to two D batteries. Measure the voltage drop across the bulb. Measure the current flowing through the bulb. Calculate the resistance of the bulb. V=2.25v; I=0.24A Homework Equations R=deltaV/I The Attempt at a Solution Is the "V" in the...

If I connect the +ve terminal of one battery to a terminal of a bulb and the other terminal of the bulb to the -ve terminal of an other battery, why doesn't it glow? There is still potential difference across the bulb's terminals and so the charge should flow.

Homework Statement Estimate how many photons of visible light (500 nm) are emitted by a 100 W Bulb. The answer on the sheet says approximately 10^{20} photons/second However when I work it out I get a slightly different answer. Homework Equations I used that 1J=1W/s or E=P/t Also Energy...

need an urgent help on filament bulb topic hi everyone i am getting stuck in this assignment on question related to filament bulb. the question goes like: is resistance and gradient inverse to one another in filament bulb and when looking at the graph (which is a curve graph).. we need to...

Homework Statement If two bulbs of power 25 watt and 100 watt each rated at 220 volts are connected in series with a supply of 440 volts. Which bulb will be fused? The Attempt at a Solution This is what I think I have to do- Find out the resistances of each bulb from the data given...

What does the brightness of a bulb depend on: power or current?

Hey all. I've got some of those newer light bulbs, the ones that are like 5-10 times more efficient than the normal ones and are usually built in a spiral shape on top of a piece which contains the electronics. Now, the issue I have is that I'm apparently getting interference or something in...

Find the root-mean-square electric field (averaged over all frequencies) at a point in space 1 meter from a 40-watt light bulb. The emitted power: P = 40 W R = 1 m Intensity: S = P/(4\piR2) S = (c/4\pi)<E2> Erms = (<E2>)1/2 Now I will set the two equal and solve for <E2>...

Homework Statement Which of the following statements about the discharging of a capacitor through a lightbulb are correct? a. Electrons in the wires flow away from the negative plate, toward the positive plate, reducing the charge on the plates. b. The electric field at a location inside...

Today in a lecture, prof asked that for 2 bulbs connected in series(100W and 40W), which was brighter? And the answer was the 40W bulb. His explanation was that we use P = I2 R. Higher power rating means higher R, and thus less bright. I argued that since P = VI, and I is constant, P is...

Homework Statement A small bulb is placed in front of a convex lens. a) Suppose that the bulb is placed as shown. Using all three principal rays, draw an accurate ray diagram to determine the location of the image. Label the image location...

Homework Statement A "90-watt" light bulb uses an average power of 90W when connected to an rms voltage of 120V . What is the resistance of the lightbulb?Homework Equations Pav=(V2rms/R) The Attempt at a Solution 90W = 120V2/R 90W/120V2 = R R = .00625\Omega

greetings, what is the meaning of a zero watt bulb?how can be any bulb glow without any power consumption? thanks

Homework Statement Homework Equations P = IV The Attempt at a Solution Part 1 For the first part I solved P = IV for the current flowing through the bulb to find that I = 0.5 A. I then divided 115 Ah by 0.5 A to get 230 hours. Now, I don't really understand what I did...

Hi! A classic example in order to demonstrate the Photoelectric Effect, is to charge a metal plate (by electrons) connected to an electroscope and observe how the charge decreases when lightning by UV light. When put a pane of glass in front of the metal plate, we observe that the charge...

This is a pretty easy problem, there is a room that is enclosed and all of the walls are opaque, there is no way to know what is going on inside from the outside (you are on the outside). There are three switches outside in which one of them has a circuit that flows to the light bulb. You can...

Hi. I seek your opinions on a "simple" circuit: -------------------------- |........|...| Voltage..... Bulb2...Bulb3 |.......|...| |....Bulb1... | Here one have a voltage (battery) and three bulbs: Bulb1, Bulb2, Bulb3. We think of the bulbs as Ohm-resistances where Bulb1 is a series...

Homework Statement greetings why a bulb glow dimmer in beginning and then brighter when it is connected to a inductor?

Why does a 220V supply current flows through the Ground(i mean Earth), whereas when i connect a 12V battery and a small LED/bulb to it and the other terminal to ground(earth), why won't the bulb glow? My question here is: If it is possible to glow a 220V rated bulb by connecting it b/w phase and...

School experiment: Shine lamp at a solar cell, and measure the voltage using a multimeter. Independent variable is the distance between the light bulb and solar cell, dependent variable is the voltage. What is the relationship between the two? And how exactly do I prove it? What I have...

what type of ray does the bulb light emit?

I have a power strip with a neon bulb that I would like to understand better. I can vary the voltage to the power strip by turning off and on an electric heater in the same room. With the heater on the voltage at the power strip reads about 125.0V on a digital volt meter. With the heater off the...

Why is a bulb lit as soon as a torch is switched on? Because I thought the electrons in the wire drift really slowly. I don't get the explanation in my textbook thanks in advance...

Homework Statement Given a 24VDC Generator, a 12VDC Battery(Discharged), a bulb(no rating yet), pieces of thick wires(unlimited length you can use) You need the 24VDC generator to charge the 12VDC battery, but direct will damage the battery. What should I do with the bulb? I need to build a...

Homework Statement On a dark night, most people can see a 100W light bulb from at least 1 km away. Given that a 100W light bulb emits about 5W of visible light, and assuming that the wavelength is 500 nm, calculate the number of photons per second entering each eye (pupil diameter 0.7 cm) of...

So when you watch those youtube videos and they put a compact fluorescent light bulb in the microwave and it starts to glow , but how come we get visible light from something that we are shooting microwaves at , it seems like conservation of energy does not hold . but then when i was...

Ok so I have a flashlight that is 19.2 volts. It used to have a bulb that was 19.2 volts and .6 amps, but I broke it, and couldn't find a replacement, so I decided to try to use an LED and a resistor. The LED is 20 mA (.02 Amps) and 3.5 Volts. If I am correct, to find the resistor I need I would...

Homework Statement A light bulb is designed for use in a 120 V circuit. If by mistake it is plugged into a 240 V circuit, what will happen to the power of the light bulb? Explain. Homework Equations I = V/R P = VI The Attempt at a Solution Since I = V/R and the resistance of the...

EDIT: NOT A HOMEWORK PROBLEM in a bulb increase in resistance means that there is a increase in brightness.if there is a decrease in resistance means that decrease in brightness. is the statement correct ? one more question does the brightness depend on current say we have same R , if i...

ok revision question fo me, just want to check my reasonning. which of te bulbs on the circuit of the attatched file will shine more brightly? i think p....because s and t r and q are in parrellel which is resistance 1/Rs+Rt+1/Rr+Rq where Rp is the sum of the resistance of 1/Rs+Rt+1/Rr+Rq...

Homework Statement What is the peak electric field 2 metres away from a 60W light bulb. Assume that the light emits light evenly in all directions (spherically uniform). Homework Equations I figure that this is to do with the poynting vector. S = \frac{1}{\mu_0}(\vec{E} \times...

Pardon me if there is an obvious answer, I have not spent too much time thinking about it. Having stumbled upon the "light cone." (Just the spacetime diagram centered around the event of turning on a light source.) I have the following question: I am not going to be too detailed, but why...

If i have a light bulb , and it has a tungsten filament and when i turn it on its gets hot , If i hook a lead to the filament and then put the anode away from the filament can i get electrons to flow through the vacuum , assuming this is done with DC current. If we used 2 different...

Homework Statement A light bulbs brightness can be measured by its power consumption. This in turn will depend on the I, V and R of the light bulb. The light bulb is rated at a power consumption of 1.0W when placed at a voltage of 6.0V. We change the battery from a 6.0V to a 3.0V one. Will...

I have two questions actually: 1. According to Stefen's Law formula power created by an conventional tungsten bulb can be calculated and temperature of the filament is about 3500 K. I know it has low pressure gas inside a bulb but doesn't that mean sooner you switched on the bulb the pressure...

I think this thing might work. It looks like it has a small opening that probably has a high potential electrode as the source of negative ions. They claim it will clean the air in a 100 square foot area...

Which bulb is brighter :) b]1. Homework Statement [/b] There is a circuit with a voltage V, and 3 identical bulbs of resistance R. B and C are parallel to each other, and A is in series to them. what happens when bulb c is removed? student one: I think that bulb B will get brighter. Bulb B...

Homework Statement An ordinary 150-Watt light bulb has a resistance of about 96 ohms. Suppose you were to connect a 2.0 V battery to such a light bulb. How much current would flow? Determine how much power the bulb would radiate? (probably too little for a person to detect). Use you own...

The interior lighting of the refrigerators is provided by incandescent lamps whose switches are actuated by the opening of the refrigerator door. Consider a refrigerator whose 30-W lightbulb remains on continuously as a result of a malfunction of the switch. If the refrigerator has a COP of...

Homework Statement A 100W bulb emits light of a single wavelength 6000*10^-10 m. If light spreads out uniformly in space, how many photons enter your eye per second if you are at a distance 1m from the bulb and the pupil diameter is about 1mm? Homework Equations E = hc/lambda The...

The room temperature resistance of the tungsten filament in an ordinary incandescent light bulb is about 1/15th of the hot resistance exhibited during the normal operation at 117 VAC. Therefore, when you throw the switch to turn on the light bulb there is a huge surge of current in excess of the...

The bulb connected to the input of a step-up transformer is less bright than a similar bulb connected to its output. Why?

Homework Statement Homework Equations KE = 1/2mv^2 F_B=I(L x B) The Attempt at a Solution I have the answer to this, (D) but I don't know how to get it. I know that the gained kinetic energy is equal to the lost potential energy of the system. What's the potential energy of...

Out of curiousity, I am wondering what happens, theoretically of course, if we place a 1.5V AC light bulb (which do not exist) onto a DC circuit with a 1.5V battery? What would happen if we connect this battery backwards on the circuit (positive to the negative terminal and vice versa). This...

Homework Statement A) How much power does a light bulb connected to a 120 V outlet use if it draws .5 A of current? Show your calculations B) One kilowatt hour is a measure of energy which is equal to 3,600,000 J. How many hours would you have to leave on the light bulb from part A...

Homework Statement "A light bulb is connected to a coil of wire. If a magnet is passed back and forth through the coil the bulb will light up. Why?"Homework Equations The Lenz Law isn't really an equation, but it states that: "The magnetic field of the induced current is in a direction to...

RC Circuit -------------------------------------------------------------------------------- Hi guys, I am trying to built an RC circuit in series to light a bulb intermitently. That is on and off in a time interval. Any ideas?

If you have a moving light bulb and an observer at rest wrt the light bulb. The observer is tiny and he is inside the light bulb. The light bulb is traveling along the x axis. The light is then turned on what will the observer see..a sphere of photons traveling outwards from the observer...