An electric light is a device that produces visible light from electric power. It is the most common form of artificial lighting and is essential to modern society, providing interior lighting for buildings and exterior light for evening and nighttime activities. In technical usage, a replaceable component that produces light from electricity is called a lamp. Lamps are commonly called light bulbs; for example, the incandescent light bulb. Lamps usually have a base made of ceramic, metal, glass, or plastic, which secures the lamp in the socket of a light fixture. The electrical connection to the socket may be made with a screw-thread base, two metal pins, two metal caps or a bayonet cap.
The three main categories of electric lights are incandescent lamps, which produce light by a filament heated white-hot by electric current, gas-discharge lamps, which produce light by means of an electric arc through a gas, such as fluorescent lamps, and LED lamps, which produce light by a flow of electrons across a band gap in a semiconductor.
Before electric lighting became common in the early 20th century, people used candles, gas lights, oil lamps, and fires. English chemist Humphry Davy developed the first incandescent light in 1802, followed by the first practical electric arc light in 1806. By the 1870s, Davy's arc lamp had been successfully commercialized, and was used to light many public spaces. Efforts by Joseph Swan and Thomas Edison
led to commercial incandescent light bulbs becoming widely available in the 1880s, and by the early twentieth century these had completely replaced arc lamps.The energy efficiency of electric lighting has increased radically since the first demonstration of arc lamps and the incandescent light bulb of the 19th century. Modern electric light sources come in a profusion of types and sizes adapted to many applications. Most modern electric lighting is powered by centrally generated electric power, but lighting may also be powered by mobile or standby electric generators or battery systems. Battery-powered light is often reserved for when and where stationary lights fail, often in the form of flashlights or electric lanterns, as well as in vehicles.
there is a 1000 light bulbs in a room
near each bulb there is a switch which turns the bulb near it on in a push of a button
and turns it off in a second push of a button and turns it on again in the third push of a button.
1000 students come into the room
the first student pushing every...
Homework Statement
I am currently carrying out an investigation into all the factors that affect the resistance of a lightbulb. Firstly, I have done a graph to show voltage against resistance for a 24W Lightbulb to see if Watts affect resistance, however my friends and teacher all told me to...
very cool. i wonder if there's a catch:
http://www.telegraph.co.uk/earth/earthnews/4375077/Scientists-invent-2-energy-saving-lightbulb-that-last-for-60-years.html
I have a plant in my living room that doesn't get much light, and so it doesn't do very well. I've always been told that light from normal lightbulbs doesn't help because it's not "natural" light. But then I started thinking. The filament glows from the current and I'm just wondering what makes...
Homework Statement
"Provide a true explanation for what you see as you look at a lightbulb underwater"
(See the attached Image)
What you see:
Out of water -> white opaque light bulb
Underwater -> clear outside, opaque white inside
Homework Equations
N/A
The Attempt at a...
You're in a room with three switches that open three lightbulbs in a separate room. You don't know which switch turns on which lightbulb. How do you find out which switch goes to which lightbulb by entering the other room only once? You don't have any help, you can't see the other room while you...
Homework Statement
The corroded contacts in a lightbulb socket have 5.0 Ohms of resistance. How much actual power is dissipated by a 100 W (120 V) lightbulb screwed into this socket?
Homework Equations
P = V^2/R
V = IR
P = RI^2
The Attempt at a Solution
I found the resistance of the lightbulb...
Homework Statement
The corroded contacts in a lightbulb socket have 8 Ω total resistance.How much actual power is dissipated by a 126 W (115 V) lightbulb screwed into the socket?
Homework Equations
P = I*V
I = E/R
The Attempt at a Solution
I = 115/8 = 14.375
I don't know how to...
[SOLVED] resistance of a lightbulb?
hey dudes
so I've a lightbulb that says 60w 230v
so i figure it draws 60/230 amps
so i figure its resistance is 60w/((60/230)^2), which gives me 882 ohms
so i checked this light bulb with a multimeter and it reads 65 ohms!
so i figure that at its...
Homework Statement
Hi,
I made a eletric generator by connecting 3 motors (R/C car motor) to a spinning wheel. Each motor can generate approx 3 volts, it can generate approx 7.5 volt when I connected them in series.
When I connect a motor output (approx 3 volt) to a flashlight light...
Homework Statement
4 identical light bulbs are connected either in series (circuit 1) or parallel (circuit 2) to a constant voltage battery with negligible internal resistance as shown.
http://img413.imageshack.us/img413/7250/seriesoz2.th.jpg...
Homework Statement
A 3-way lightbulb can produce 50W, 100W or 150W at 120V. Such a bulb contains 2 filaments that can be connected to the 120V individually or in parallel.
a) describe how the connections to the 2 filaments are made to give each of the 3 wattages
b) What can be the...
Homework Statement
You have a large supply of lightbulbs and a single battery. You start with one lightbulb connected to the battery and notice its brightness. You then add one lightbulb at a time, each new lightbulb being added in parallel to the previous lightbulbs. As the lightbulbs...
Homework Statement
Consider the simple circuit shown below, in which a light bulb with resistance R and a capacitor with capacitance C are connected in series with a battery and an open switch. The capacitor has a large capacitance and is initially uncharged. The battery provides enough power...
This probability problem is for my calculus class...
a) A type of lightbulb is labeled as having an average lifetime of 1000 hours. It's reasonable to model the probability of failure of these bulbs by an exponential density function with mean = 1000. Use this model to find the probability...
I'm reading SpaceTime Physics by John Wheeler (not for school) and came across a problem that doesn't have answer in the back so i want to see if i understood it properly. the problem goes like this:
You have two parallel wires with a battery and lighbulb connecting one end. on top of the two...
what is the electric field 1m away from a 100 watt light bulb
i know that the power of the light bulb 100 watt = volts x amps
so if the light bulb is a standard 120 volts then the electric field would be V / r
im not sure about this because i know the electric field radiating...
So i was checking out some lightbulbs a while back and i noticed they had these numbers on it. One type had the number... it was like 3100K and the other was 5500K or so. Are these the temperatures corrposponding to the blackbody radiation associated with those temperatures? I know there's 2...
Suppose the light bulb in Figure 22.4b is a 60.0-W bulb with a resistance of 240 W. The magnetic field has a magnitude of 0.40 T, and the length of the rod is 0.60 m. The only resistance in the circuit is that due to the bulb. Minimally, how long would the rails on which the moving rod slides...