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The lighting industry in the United States is in the middle of a huge transition. Incandescent light bulbs used to be the norm, but they are not very environmentally friendly. Research has produced two types of greener light bulbs: the Compact Fluorescent Light (CFL) and the Light-Emitting Diode (LED). CFL bulbs are not nearly as efficient as LED’s, and are thought of more as a temporary solution to energy-efficient lighting. While LED’s are much more efficient than incandescent or CFL bulbs, there is still room to make them even more efficient. Your challenge is to determine how efficient these different light bulbs are and how they affect the planet. In doing this, you can help save our planet one step at a time.

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What are some different types of light bulbs?

Incandescent bulbs are the most popular type of light bulb. They consist of a thin piece of tungsten metal, called the filament, coiled inside of a glass bulb. The filament is held up by a glass support and is connected to electrical contacts. When electricity flows through the filament, it heats it up to 4,000 degrees Fahrenheit so that the filament produces light. Inside the glass bulb is an inert gas (usually argon) to help keep the filament from catching on fire (if there is no oxygen inside the bulb, then there can't be a fire). Halogen light bulbs are very similar to incandescent bulbs, but they have a few key differences. The bulb in a halogen light is made of quartz, and is much smaller than an incandescent bulb. Also, the gas inside the bulb is not an inert gas, but a gas from the halogen group. Halogen gases can combine with tungsten atoms that evaporate from the filament and redeposit them on the filament, making the light last longer. The filament can also run hotter than incandescent bulbs, which means that you can get more light for the same amount of energy. However, this also means that halogen lights are much hotter than incandescent lights. Fluorescent light bulbs come in many shapes, but the basic design is a glass tube with electrodes on each end. The tube is filled with an inert gas (usually argon) and a small amount of mercury. When a current is run through the tube, the mercury emits ultraviolet light. Phosphors, which are things that emit light when exposed to light, are dusted along the inside of the tube in the form of a powder. The phosphors fluoresce when exposed to the ultraviolet light and produce visible light, which is the light that we see fluorescent lights produce. Compact fluorescent lamps have a glass tube that is twisted into a spiral so that they take up approximately the same amount of space of an incandescent bulb. A drawback of fluorescent lights is that they take a few seconds to warm up before they can emit 100% of the light that they are capable of. In Light Emitting Diodes, electron movement is converted directly to light, with very little of the energy being converted into heat. Because of this, they have the lowest operating temperature of the major types of light bulbs. LED's have many advantages over incandescent and fluorescent lights. Since there is no filament, there is no way for them to burn out. Additionally, they are much more energy efficient; incandescent bulbs typically produce 17 lumens per Watt of electricity, CFL's produce 50-70 lumens per Watt, and LED's produce around 112 lumens per Watt. LED's can last for 50,000 hours, compared to 1,000 to 2,000 or almost six years; almost eight times as long as CFL's, which typically last for 10,000 hours. Incandescent bulbs only last an average of 1,000 hours.

Why are incandescent bulbs so popular?

Since being invented in the early 1800s, incandescent light bulbs have been and still are the most popular type of lighting used throughout the world. They are simple to install and use, and are very cheap. They work well with both AC and DC power, so they can be used in almost any situation, from house lighting to flashlights. Also, many people like the tone of light that incandescent bulbs emit.

Why are CFL bulbs considered to be transition bulbs?

While CFL bulbs are much more efficient than incandescent bulbs, they are not nearly as green as LED's. CFL's use much more energy than LED's do to produce the same amount of light, and don't last nearly as long. In addition, CFL's include a small amount of mercury that can be released if the bulb is broken. Mercury is very toxic, and CFL bulbs must be disposed of as hazardous waste. For these reasons, CFL's are seen as a temporary solution until greener lighting technology can become more widespread.

How do you calculate the cost of using different bulbs?

To calculate the cost of using a certain type of bulb, you must first find the Kilowatt hours (kWh) that the bulb will use. To find this, multiply the wattage of the bulb by the number of hours it will be running, and divide by 1,000. kWh =
× hours run
The cost of operating the bulb is the kWh that the bulb will use multiplied by the price of electricity per kWh: Cost of operation = kWh × price per kWh To find the initial cost of the light bulbs themselves, multiply the number of bulbs needed by the price of each bulb: Initial cost = number of bulbs × price per bulb To find the total cost of the lighting, add the cost of operation and the initial cost: Total Cost =
× hours run × price per kWh + (number of bulbs × price per bulb)
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