Quiz: What You Don't Know About Energy-Efficient Lighting
Thermal image by Tyrone Turner, National Geographic
You know new light bulb rules are going into effect in many countries, but how much do you really know about the energy used to brighten your world?
Thomas Edison is credited far and wide with "invention" of the incandescent light bulb. But what scientist reported success with just such an innovation a year before Edison did?
- Humphry Davy
- Michael Faraday
- Albert Einstein
- Joseph Swan
In 1878, British scientist Sir Joseph Wilson Swan reported success producing short-lived light from a carbon filament lamp. But Edison showed a high-resistance thin filament could produce light for many hours. After squabbles in the British courts, the two scientists teamed together to sell lamps from a joint company, "Ediswan."
The first spiral compact fluorescent light bulbs (CFL) appeared on the market in 1995. But when was the design invented?
In 1976, in the wake of the Arab oil embargo and energy crisis, General Electric engineer Edward Hammer developed the spiral CFL in a company lab in Ohio. GE thought it would be too expensive and shelved the idea until other companies brought it to market two decades later.
Energy Star-rated CFLs use approximately how much less energy than an equivalent incandescent (standard) light bulb?
- 25 percent
- 50 percent
- 75 percent
- 100 percent
CFLs typically use about 75 percent less energy than incandescent bulbs to produce roughly the same amount of light. In incandescent bulbs, much of the energy is lost as heat.
Which country was the first to phase out incandescent light bulbs?
- The United States
To capture the energy savings CFLs offer, Cuba led the world in phasing out incandescent bulbs in 2006. Social workers visited households all over the country, replaced incandescents with CFLs free of charge, and destroyed the replaced lamps to remove them from service.
What does the Kelvin measurement of a light bulb mean?
- How much energy the bulb uses.
- How hot the bulb gets.
- What lifespan the bulb can be expected to achieve
- What color light the bulb gives off
In lighting, Kelvin is a measurement of "color temperature." It is sometimes confusing because higher temperatures (3,600-5,500K) give off "cooler" blue-green colors while lower temperatures (2,700-3,000K) give off the yellow-red colors considered "warm."
Frequent on-off switching (five-minute cycles or less) can decrease the lifespan of a CFL up to how much?
- 25 percent
- 45 percent
- 65 percent
- 85 percent
Lighting studies show frequent switching reduces a CFL's lifespan 85 percent, cutting it so short that it will last no longer than an incandescent bulb. Some studies have estimated that the average CFL should be good for about 7,000 on-off cycles.
To produce light efficiently, CFL bulbs rely on mercury sealed in a glass tube. The same toxic metallic element is used in the glass "fever" thermometers that have been mostly replaced by digital technology. Which of the following statements about their mercury contents is true?
- Glass thermometers contain as much mercury as in 125 CFLs.
- CFLs contain as much mercury as in 125 glass thermometers.
- Glass thermometers contain half the mercury of a CFL.
- A CFL contains half the mercury of a glass thermometer.
The average CFL contains about 4 milligrams (mg) of mercury, and it would take 125 to add up to the 500 mg contained in a glass thermometer. Some newer model CFLs contain as low as 1 mg of mercury.
All of the following are advantages of light-emitting diodes (LEDs) EXCEPT:
- LEDs cost half as much as incandescents for the same light output.
- LEDs typically use 90 to 95 percent less energy than incandescents for the same light output.
- LEDs often come with estimated lifespans of 10 to 20 years and tens of thousands of hours of use.
- LEDs work great for rapid on-off switching.
LEDs currently cost far more than incandescents for an equivalent light output. Prices for LEDs have been falling sharply in recent years, but in 2011 bulbs remained in the $20 to $50 range.
What is the internationally recognized unit for brightness of a light source (in other words, the light source's perceived power)?
- Color temperature
Lumens are the standardized unit for how bright a light source is. In the age of the incandescent bulb, people became accustomed to using watts as an approximation, but that measure isn't useful when it comes to technologies like CFLs and LEDs that achieve brightness at low wattage.
True or False? The new lighting standards that the United States will phase in beginning on January 1, 2012, will force U.S. consumers to use CFLs or LEDs.
False. Manufacturers already are selling advanced halogen bulbs, a type of incandescent that meets the new requirement of delivering the light of traditional incandescent bulbs at lower wattage. Further advances are expected.
Halogen bulbs are not as efficient as CFLs, but they do represent an energy savings over traditional incandescents. But what is a disadvantage of halogen bulbs?
- They don't last as long as traditional incandescents.
- They give off a colder light.
- They operate at higher temperatures than traditional incandescent.
- They contain mercury.
Halogens typically operate at higher temperatures than traditional incandescent and must be handled carefully. But they don't contain mercury as CFLs do, and they last longer than traditional incandescents while providing the same warm light.
All of the following lighting technologies can help reduce energy use except:
- Recessed lights
- Motion sensors
- Low-voltage lighting
Recessed lights are only as efficient as the bulbs that are chosen for the fixture. Dimmers, motion sensors and low-voltage lighting are all strategies that can help save energy, however.
Great work! You are especially "bright" when it comes to energy-efficient lighting.
Luminous score! See how your knowledge glows when you take the quiz again.
Could be better. See if another try on the quiz provides some illumination.
Brush up on your lighting and energy facts at The Great Energy Challenge, and then retake the quiz to see how much you've learned.Retake Quiz
More Energy Quizzes
You know that poor insulation makes for a drafty, energy-wasting home, but how much do you really know about the true potential of energy efficiency?
You know that demand in Asia is moving energy markets around the world, but how much do you really know about the needs and resources of the world's most populous continent?
Historians say the modern era of energy began on October 17, 1973, when Arab exporters unleashed the "oil weapon" with an embargo against the United States and its allies. How much do you know about the global oil shocks of the past 40 years and how they changed the world?
Every few years, the Intergovernmental Panel on Climate Change (IPCC) releases a new summary of the scientific consensus on climate change. How much do you know about the forces altering the Earth's temperature, according to the IPCC's September 2013 report?
You know that climate change is reshaping the Arctic, but how much do you really know about how shrinking sea ice is opening up the resources at the top of the world for exploration and development?
Great Energy Challenge Blog
@NatGeoGreen on TwitterTweets by @NatGeoGreen
Great Energy Challenge Blog
Working Toward Smarter Cities
From better mass transit to a stronger mix of renewable energy, what is the most important thing we can do to make cities smarter when it comes to energy use?
Istanbul, the only city in the world that spans two continents, is a perfect setting for a close look at the energy and sustainability challenges of our increasingly urban planet.