Incandescent lightbulbs

Use a Flinn C-Spectra to view an incandescent lightbulb. What do you observe Draw the spectrum using colored pencils. 

Wait several minutes to allow the incandescent lightbulb and the spectrum tubes to cool. 

He decided that the material the world needed most was a synthetic shellac to replace the natural shellac produced from the resinous secretions of the lac beetle native to southeastern Asia. At the time, shellac was the optimal insulator for electrical wires. Ever since Edison s 1879 invention of the incandescent lightbulb, miles of shellac-coated metal wire were being stretched across the land. The supply of shellac, however, was unable to keep up with demand. 

How much money would you save per hour by replacing a 100-watt incandescent lightbulb with an equally bright 20-watt fluorescent bulb Assume the cost of electricity to be 15 cents per kilowatt-hour. 

The savings for each hour is the difference 1.5 cents minus 0.3 cents, which equals 1.2 cents per hour. This may not sound like much, but if 50 million households in the United States changed just one of their lightbulbs from a 100-watt incandescent to a 20-watt fluorescent, then the total annual savings would be on the order of 1.2 billion dollars. 

A 100-W incandescent lightbulb produces around 15 lumens per watt (lm/W), standard fluorescent lights produce up to lOOlm/W, while commercial LEDs have reached 65 lm/W. LEDs can easily last 100,000 hours. 

I The temperature of the filament of an incandescent lightbulb is 2500 K. As-I suming the filament to be a blackbody, determine the fraction of the radiant energy emitted by the filament that falls in the visible range. Also, determine I the wavelength at which the emission of radiation from the filament peaks. 

SOLUTION the temperature of the filament of an incandescent lightbulb Is given. The fraction of visible radiation emitted by the filament and the wavelength at vdiich the emission peaks are to be determined. 

An incandescent lightbulb is desired to emit at least 15 percent of its energy al wavelengths shorter than 0.8 pm. Determine the minimum temperature to which the filament of the lightbulb must be heated. 

Argon is used in various types of lightbulbs, including incandescent and compact fluorescent (shown here). IMAGE COPYRIGHT 2007, R. MACKAY. USED UNDER LICENSE FROM SHUTTERSTOCK.COM. 

The tungsten filament in an incandescent lightbulb ordinarily operates at a temperature of about 2500°C. At this temperature, the vapor pressure of solid tungsten is 7.0 X 10 atm. Estimate the number of gaseous tungsten atoms per cubic centimeter under these conditions. 

Incandescent lightbulbs are filled with noble gases, usually argon and krypton, to protect the filament. The tungsten filament gets so hot that it will react with all but the most inert elements. 

Tungsten (W) is used as a filament in incandescent lightbulbs because it has a high melting point, 3420°C, and boiling point, 5850°C. But, nothing lasts forever. Because electricity continuahy passes through the filament, the metal eventuahy breaks as it vaporizes, and the bulb burns out. 

Switch from incandescent lightbulbs to compact fluores-... 

Along with chemical reactions, applications form an important part of descriptive chemistry. Because students are interested in chemistry s impact on their lives, we have included many new "Chemistry in Focus" boxes, which describe current applications of chemistry. These special interest boxes cover such topics as new technology to replace the incandescent lightbulb, using bees to detect drugs and bombs at airports, and analyzing isotopes in human hair to identify disaster victims country of origin. 

A watt is a measure of power (the rate of energy change) equal to 1 J/s. (a) Calculate the number of joules in a kilowatt-hour, (b) An adult person radiates heat to the surrounding at about the same rate as a 100-watt electric incandescent lightbulb. What is the total amount of energy in kcal radiated to the surroundings by an adult in 24 hours ... 

Figure 13-6 shows an argon atom. Argon, a gas in its natural state, has 18 total electrons and 8 electrons in its outer orbit, and thus no free electrons. This makes it very difficult for electrons to flow from one argon atom to another. Because argon gas is an excellent insulator, it is used to encase the filament of incandescent lightbulbs. 

Because the LED is a diode, connecting it to the correct positive or negative terminal is very important. Figure 15-19 notes two methods for determining how to connect the LED. The positive terminal is called the anode and has a longer lead. The negative side of the LED, termed the cathode, has a flat surface in the plastic cover. Because the LED does not have a filament that would burn out because of heat like the traditional incandescent lightbulb, the LED has an unlimited life span. 

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