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More than 150 years ago, inventors began working on a bright idea that would have a dramatic impact on how we use energy in our homes and offices. This invention changed the way we design buildings, increased the length of the average workday and jumpstarted new businesses. It also led to new energy breakthroughs -- from power plants and electric transmission lines to home appliances and electric motors.

Like all great inventions, the light bulb can't be credited to one inventor. It was a series of small improvements on the ideas of previous inventors that have led to the light bulbs we use in our homes today.

Incandescent Bulbs Light the Way

Long before Thomas Edison patented -- first in 1879 and then a year later in 1880 -- and began commercializing his incandescent light bulb, British inventors were demonstrating that electric light was possible with the arc lamp. In 1835, the first constant electric light was demonstrated, and for the next 40 years, scientists around the world worked on the incandescent lamp, tinkering with the filament (the part of the bulb that produces light when heated by an electrical current) and the bulb's atmosphere (whether air is vacuumed out of the bulb or it is filled with an inert gas to prevent the filament from oxidizing and burning out). These early bulbs had extremely short lifespans, were too expensive to produce or used too much energy.

When Edison and his researchers at Menlo Park came onto the lighting scene, they focused on improving the filament -- first testing carbon, then platinum, before finally returning to a carbon filament. By October 1879, Edison's team had produced a light bulb with a carbonized filament of uncoated cotton thread that could last for 14.5 hours. They continued to experiment with the filament until settling on one made from bamboo that gave Edison's lamps a lifetime of up to 1,200 hours -- this filament became the standard for the Edison bulb for the next 10 years. Edison also made other improvements to the light bulb, including creating a better vacuum pump to fully remove the air from the bulb and developing the Edison screw (what is now the standard socket fittings for light bulbs).

(Historical footnote: One can't talk about the history of the light bulb without mentioning William Sawyer and Albon Man, who received a U.S. patent for the incandescent lamp, and Joseph Swan, who patented his light bulb in England. There was debate on whether Edison's light bulb patents infringed on these other inventors' patents. Eventually Edison's U.S. lighting company merged with the Thomson-Houston Electric Company -- the company making incandescent bulbs under the Sawyer-Man patent -- to form General Electric, and Edison's English lighting company merged with Joseph Swan's company to form Ediswan in England.)

What makes Edison's contribution to electric lighting so extraordinary is that he didn't stop with improving the bulb -- he developed a whole suite of inventions that made the use of light bulbs practical. Edison modeled his lighting technology on the existing gas lighting system. In 1882 with the Holborn Viaduct in London, he demonstrated that electricity could be distributed from a centrally located generator through a series of wires and tubes (also called conduits). Simultaneously, he focused on improving the generation of electricity, developing the first commercial power utility called the Pearl Street Station in lower Manhattan. And to track how much electricity each customer was using, Edison developed the first electric meter.

While Edison was working on the whole lighting system, other inventors were continuing to make small advances, improving the filament manufacturing process and the efficiency of the bulb. The next big change in the incandescent bulb came with the invention of the tungsten filament by European inventors in 1904. These new tungsten filament bulbs lasted longer and had a brighter light compared to the carbon filament bulbs. In 1913, Irving Langmuir figured out that placing an inert gas like nitrogen inside the bulb doubled its efficiency. Scientists continued to make improvements over the next 40 years that reduced the cost and increased the efficiency of the incandescent bulb. But by the 1950s, researchers still had only figured out how to convert about 10 percent of the energy the incandescent bulb used into light and began to focus their energy on other lighting solutions.

Energy Shortages Lead to Fluorescent Breakthroughs

In the 19th century, two Germans -- glassblower Heinrich Geissler and physician Julius Plücker -- discovered that they could produce light by removing almost all of the air from a long glass tube and passing an electrical current through it, an invention that became known as the Geissler tube. A type of discharge lamp, these lights didn't gain popularity until the early 20th century when researchers began looking for a way to improve lighting efficiency. Discharge lamps became the basis of many lighting technologies, including neon lights, low-pressure sodium lamps (the type used in outdoor lighting such as streetlamps) and fluorescent lights.

Both Thomas Edison and Nikola Tesla experimented with fluorescent lamps in the 1890s, but neither ever commercially produced them. Instead, it was Peter Cooper Hewitt's breakthrough in the early 1900s that became one of the precursors to the fluorescent lamp. Hewitt created a blue-green light by passing an electric current through mercury vapor and incorporating a ballast (a device connected to the light bulb that regulates the flow of current through the tube). While the Cooper Hewitt lamps were more efficient than incandescent bulbs, they had few suitable uses because of the color of the light.

By the late 1920s and early 1930s, European researchers were doing experiments with neon tubes coated with phosphors (a material that absorbs ultraviolet light and converts the invisible light into useful white light). These findings sparked fluorescent lamp research programs in the U.S., and by the mid and late 1930s, American lighting companies were demonstrating fluorescent lights to the U.S. Navy and at the 1939 New York World's Fair. These lights lasted longer and were about three times more efficient than incandescent bulbs. The need for energy-efficient lighting American war plants led to the rapid adoption of fluorescents, and by 1951, more light in the U.S. was being produced by linear fluorescent lamps.

It was another energy shortage -- the 1973 oil crisis -- that caused lighting engineers to develop a fluorescent bulb that could be used in residential applications. In 1974, researchers at Sylvania started investigating how they could miniaturize the ballast and tuck it into the lamp. While they developed a patent for their bulb, they couldn't find a way to produce it feasibly. Two years later in 1976, Edward Hammer at General Electric figured out how to bend the fluorescent tube into a spiral shape, creating the first compact fluorescent light (CFL). Like Sylvania, General Electric shelved this design because the new machinery needed to mass-produce these lights was too expensive.

Early CFLs hit the market in the mid-1980s at retail prices of $25-35, but prices could vary widely by region because of the different promotions carried out by utility companies. Consumers pointed to the high price as their number one obstacle in purchasing CFLs. There were other problems -- many CFLs of 1990 were big and bulky, they didn't fit well into fixtures, and they had low light output and inconsistent performance. Since the 1990s, improvements in CFL performance, price, efficiency (they use about 75 percent less energy than incandescents) and lifetime (they last about 10 times longer) have made them a viable option for both renters and homeowners. Nearly 30 years after CFLs were first introduced on the market, an ENERGY STAR® CFL costs as little as $1.74 per bulb when purchased in a four-pack.

LEDs: The Future is Here

One of the fastest developing lighting technologies today is the light-emitting diode (or LED). A type of solid-state lighting, LEDs use a semiconductor to convert electricity into light, are often small in area (less than 1 square millimeter) and emit light in a specific direction, reducing the need for reflectors and diffusers that can trap light.

They are also the most efficient lights on the market. Also called luminous efficacy, a light bulb's efficiency is a measure of emitted light (lumens) divided by power it draws (watts). A bulb that is 100 percent efficient at converting energy into light would have an efficacy of 683 lm/W. To put this in context, a 60- to 100-watt incandescent bulb has an efficacy of 15 lm/W, an equivalent CFL has an efficacy of 73 lm/W, and current LED-based replacement bulbs on the market range from 70-120 lm/W with an average efficacy of 85 lm/W.

In 1962 while working for General Electric, Nick Holonyak, Jr., invented the first visible-spectrum LED in the form of red diodes. Pale yellow and green diodes were invented next. As companies continued to improve red diodes and their manufacturing, they began appearing as indicator lights and calculator displays in the 1970s. The invention of the blue diode in the 1990s quickly led to the discovery of white LEDs -- researchers simply coated the blue diodes with a phosphor to make it appear white. Shortly thereafter, researchers demonstrated white light using red, green and blue LEDs. These breakthroughs led to LEDs being used in a variety of applications including traffic lights, flashlights and TVs.

To make LEDs an option for general lighting, researchers next had to focus on improving the efficiency of LEDs -- which in the beginning were no more efficient than incandescent bulbs. In 2000, the Energy Department partnered with private industry to push white LED technology forward by creating a high-efficiency device that packaged LEDs together.

When the Department announced the L Prize competition in 2008 (a competition designed to spur the development of ultra-efficient solid-state lighting products to replace common lighting technologies), there were just a few LED bulbs on the market that could serve as a replacement for incandescents, and most were 25-40 watt equivalents. In late 2009, Philips Lighting North America entered its LED bulb in the L Prize 60-watt replacement category. (Why focus on this type of bulb? In 2010, the Department estimated there were approximately 971 million 60-watt incandescent bulbs in use.) After a rigorous evaluation process, including testing by independent laboratories and field assessments, the Energy Department announced that Philips Lighting North America won the first L Prize in 2011. The ability to hit the tough L Prize performance targets showed it could be done and drove others in the market to strive higher.

Lighting companies continued to make improvements to both the quality of light and the energy efficiency of LEDs while cutting their costs. Since 2008, the cost of LED bulbs has fallen more than 85 percent, and most recently, a number of retailers announced that they will sell LEDs at $10 or less. Today's LED bulbs are also six to seven times more energy efficient than conventional incandescent lights, cut energy use by more than 80 percent and can last more than 25 times longer. Taken together, these advancements have led to rapid deployment in the past of couple years in both commercial and residential applications. In 2012 alone, more than 49 million LEDs were installed in the U.S. -- saving about $675 million in annual energy costs -- and as prices continue to drop, LEDs are expected to become a common feature in homes across the country.

Incandescents and existing lighting fixtures use designs that date back to Edison's days. Replacing the old bulbs with LEDs is only the tip of the iceberg when it comes to saving energy on lighting. LED lighting systems designed to take full advantage of LED's strengths have even greater energy-savings potential than forcing LEDs into 19th century fixtures.

It's hard to tell where lighting technology will go in the future, but one thing is clear: it won't be your grandfather's light bulb.

To learn how the Energy Department is working to accelerate the efficiency and quality of LEDs, visit the Solid-State Lighting Program's website.

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More than 150 years ago, inventors began working on a bright idea that would have a dramatic impact on how we use energy in our homes and offices. This invention changed the way we design buildings, increased the length of the average workday and jumpstarted new businesses.

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The inventors' battle over the delivery of electricity was an epic power play

smithsonian.com

Steve Jobs and Bill Gates. They were genius rivals: two American titans who transformed the technology industry and lived to see their visions of computers and electronic devices in billions of homes and offices around the world. Still, their philosophies and personalities were as different as night and day, or Macs and PCs, and over the years, they could not resist needling and antagonizing each other as they staked their claims in the global technology marketplace.

"The only problem with Microsoft is they just have no taste," Jobs famously said in 1996. "They have absolutely no taste. And I don't mean that in a small way, I mean that in a big way, in the sense that they don't think of original ideas, and they don't bring much culture to their products."

In 2006, when Apple released its popular Mac vs. PC ads, wherein a hip young Jobs-like character interacts with a bumbling, back-office, brown-suited Gates type, Gates was clearly irritated. "I don't know why acting like it's superior. I don't even get it," Gates said. "If you just want to say, 'Steve Jobs invented the world, and then the rest of us came along,' that's fine."

Yet despite the barbs, (and occasional lawsuits) and despite the obvious competition, both Jobs and Gates were smart enough to know that there was room in the consumer market for Apple and Microsoft to coexist, and over the years, neither was too proud or too stung by the other's words to stop them from entering into various partnerships along the way. (In fact, in 1997 Microsoft infused Apple with $150 million in cash at a time when Jobs was brought back by the board of directors to serve as interim CEO, as Apple was suffering crippling financial losses.) The same, however, cannot be said for Thomas Edison and George Westinghouse, who, more than a century ago, engaged in a nasty battle over alternating and direct current, known as the "War of Currents." Both men knew there was room for but one American electricity system, and Edison set out to ruin Westinghouse in "a great political, legal and marketing game" that saw the famous inventor stage publicity events where dogs, horses and even an elephant were killed using Westinghouse's alternating current. The two men would play out their battle on the front pages of newspapers and in the Supreme Court, in the country's first attempt to execute a human being with electricity.

After Edison developed the first practical incandescent light bulb in 1879, supported by his own direct current electrical system, the rush to build hydroelectric plants to generate DC power in cities across the United States practically guaranteed Edison a fortune in patent royalties. But early on, Edison recognized the limitations of DC power. It was very difficult to transmit over distances without a significant loss of energy, and the inventor turned to a 28-year-old Serbian mathematician and engineer whom he'd recently hired at Edison Machine Works to help solve the problem. Nikola Tesla claimed that Edison even offered him significant compensation if he could design a more practical form of power transmission. Tesla accepted the challenge. With a background in mathematics that his inventor boss did not have, he set out to redesign Edison's DC generators. The future of electric distribution, Tesla told Edison, was in alternating current-where high-voltage energy could be transmitted over long distances using lower current-miles beyond generating plants, allowing a much more efficient delivery system. Edison dismissed Tesla's ideas as "splendid" but "utterly impractical." Tesla was crushed and claimed that Edison not only refused to consider AC power, but also declined to compensate him properly for his work. Tesla left Edison in 1885 and set out to raise capital on his own for Tesla Electric Light & Manufacturing, even digging ditches for the Edison Company to pay his bills in the interim, until the industrialist George Westinghouse at Westinghouse Electric & Manufacturing Company, a believer in AC power, bought some of Tesla's patents and set about commercializing the system so as to take electric light to something more than an urban luxury service. While Tesla's ideas and ambitions might be brushed aside, Westinghouse had both ambition and capital, and Edison immediately recognized the threat to his business.

Within a year, Westinghouse Electric began installing its own AC generators around the country, focusing mostly on the less populated areas that Edison's system could not reach. But Westinghouse was also making headway in cities like New Orleans, selling electricity at a loss in order to cut into Edison's business. By 1887, after only a year in the business, Westinghouse had already more than half as many generating stations as Edison. The concern at Edison was palpable, as sales agents around the country were demoralized by Westinghouse's reach into rural and suburban areas. But Thomas Edison had an idea. Surely Westinghouse's system must be more dangerous, what with all that voltage passing through the wires. "Just as certain as death," Edison predicted, "Westinghouse will kill a customer within 6 months after he puts in a system of any size."

In November 1887, Edison received a letter from a dentist in Buffalo, New York, who was trying to develop a more humane method of execution than hanging. Having witnessed a drunk man accidentally kill himself by touching a live electric generator, Alfred P. Southwick became convinced that electricity could provide a quicker, less painful alternative for criminals condemned to death. Perhaps the Wizard of Menlo Park might have some thoughts about the best electric current "to produce death with certainty in all cases." Edison, who opposed capital punishment, at first declined to get involved with Southwick's project. But when the dentist persisted, Edison, recognizing the opportunity that had landed in his lap, wrote back to say that although he would "join heartily in an effort to totally abolish capital punishment," he did have some thoughts about electric currents in which to dispose of "criminals under sentence of death."

"The most effective of these," he wrote, "are known as 'alternating machines,' manufactured principally in this country by Mr. Geo. Westinghouse, Pittsburgh."

In June 1888, Edison began to demonstrate the lethal power of alternating current for reporters. He rigged a sheet of tin to an AC dynamo and led a dog onto the tin to drink from a metal pan. Once the dog touched the metal surface, it yelped and"the little cur dog fell dead."

Electricity will kill a man "in the ten-thousandth part of a second," Edison told one reporter shortly after the demonstration, and he was quick to remind him that "the current should come from an alternating machine."

The battle of the currents had begun. Westinghouse recognized what Edison was up to and wrote the inventor a letter, stating, "I believe there has been a systemic attempt on the part of some people to do a great deal of mischeaf and creat as great a difference as possible between the Edison Company and The Westinghouse Electric Co., when there ought to be an entirely different condition of affairs." Edison saw no reason to cooperate, and he continued his experiments at varying levels of voltage with dozens of stray dogs purchased from neighborhood boys in Orange, New Jersey at 25 cents each. Edison's research was soon proving that alternating current was, as he said, "beyond all doubt more fatal than the continuous current." By the end of the year, Edison arranged a demonstration before a New York State committee impaneled to investigate the use of electricity in executions. At his West Orange laboratory, the inventor wired electrodes to several calves and a horse; even though the animals' deaths were not quick, the committee was impressed. New York State expressed a desire to purchase "three Westinghouse alternating-current dynamos," but Westinghouse refused to sell them for the purpose of what was now being described as "electrocution." It did not matter. An electricity salesman named Harold Brown was commissioned by the state to build an electric chair, and Edison was paying him behind the scenes to use alternating current in his design. Somehow, Brown got his hands on some AC dynamos.

When New York State sentenced convicted murderer William Kemmler to death, he was slated to become the first man to be executed in an electric chair. Killing criminals with electricity "is a good idea," Edison said at the time. "It will be so quick that the criminal can't suffer much." He even introduced a new word to the American public, which was becoming more and more concerned by the dangers of electricity. The convicted criminals would be "Westinghoused."

Westinghouse was livid. He faced millions of dollars in losses if Edison's propaganda campaign convinced the public that his AC current would be lethal to homeowners. Westinghouse contributed $100,000 toward legal fees for Kemmler's appeal to the U.S. Supreme Court, where it was argued that death in the electric chair amounted to cruel and unusual punishment. Both Kemmler and Westinghouse were unsuccessful, and on August 6, 1890, Kemmler was strapped into Harold Brown's chair at Auburn prison and wired to an AC dynamo. When the current hit him, Kemmler's fist clenched so tight that blood began to trickle from his palm down the arm of the chair. His face contorted, and after 17 seconds, the power was shut down. Arthur Southwick, "the father of the electric chair," was in attendance and proclaimed to the witnesses, "This is the culmination of ten years work and study. We live in a higher civilization today."

Yet behind the dentist, Kemmler began to shriek for air.

"Great God! He's alive!" someone shouted.

"Turn on the current! Turn on the current instantly!" another screamed. "This man is not dead!"

But the dynamo needed time to build its current, and Kemmler wheezed and gasped before the horrified witnesses as the electricity began to course through his body. Some witnesses fainted while others vomited, as it appeared that Kemmler was on the verge of regaining consciousness. The back of his coat briefly caught fire. Minutes passed until Kemmler finally went rigid. The current stopped and he was pronounced dead by Dr. Edward Spitzka, who predicted, "there will never be another electrocution."

Westinghouse was horrified by the reports of Kemmler's execution. "It has been a brutal affair," he said. "They could have done better with an ax."

Sources
Thomas Edison believed that future executions by AC current would go more smoothly, "without the scene at Auburn today." To further demonstrate the lethal nature of alternating current, he held a widely attended spectacle in Coney Island, New York, where a circus elephant named Topsy was to be executed after she was deemed to be too dangerous to be around people. The elephant had killed three men in recent years-one a trainer who had tried to feed Topsy a lit cigarette. Edison had Topsy fitted with copper-wire sandals, and before a crowd of thousands, an AC current of 6,000 volts was sent coursing through the elephant until she toppled to her side, dead.

Despite all of Edison's efforts, and despite his attempts to persuade General Electric otherwise, the superiority of the AC current was too much for Edison and his DC system to overcome. In 1893, Westinghouse was awarded the contract to light the Chicago World's Fair, bringing all the positive publicity he would need to make alternating current the industry standard. For his part, Edison later admitted that he regretted not taking Tesla's advice.

Books: Mark Essig, Edison & The Electric Chair, Walker and Company, 2003. Craig Brandon, The Electric Chair: An Unnatural American History, McFarland & Company, Inc., 1999. Gilbert King, The Execution of Willie Francis: Race, Murder, and the Search for Justice in the American South, Basic Civitas Books, 2008.

Articles: ""Wait Till the NEXT One!" Newsweek, February 11, 2007. http://www.thedailybeast.com/newsweek/2007/02/12/wait-till-the-next-one.html Creating Jobs" by Steve Lohr, New York Times, January 12, 1997. "Steve Jobs and Bill Gates: It's Complicated" by Jay Greene, CNET News, Microsoft, August 24, 2011. "Coney Elephant Killed" New York Times, January 6, 1903.

About Gilbert King

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Edison vs. Westinghouse: A Shocking Rivalry

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smithsonian.com Steve Jobs and Bill Gates. They were genius rivals: two American titans who transformed the technology industry and lived to see their visions of computers and electronic devices in billions of homes and offices around the world.

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screenshots of the final score must be retainedfor submission

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Each interactive concept-builder presents learners with carefully crafted questions that target various aspects of a discrete concept. There are typically multiple levels of difficulty and an effort to track learner progress at each level. Question-specific help is provided for the struggling learner; such help consists of short explanations of how to approach the situation.

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PARTS AND MATERIALS

Multimeter, digital or analog

Assorted batteries

One light-emitting diode (Radio Shack catalog # 276-026 or equivalent)

Small "hobby" motor, permanent-magnet type (Radio Shack catalog # 273-223 or equivalent)

Two jumper wires with "alligator clip" ends (Radio Shack catalog # 278-1156, 278-1157, or equivalent)

A multimeter is an electrical instrument capable of measuring voltage, current, and resistance. Digital multimeters have numerical displays, like digital clocks, for indicating the quantity of voltage, current, or resistance. Analog multimeters indicate these quantities by means of a moving pointer over a printed scale.

Analog multimeters tend to be less expensive than digital multimeters, and more beneficial as learning tools for the first-time student of electricity. I strongly recommend purchasing an analog multimeter before purchasing a digital multimeter, but to eventually have both in your tool kit for these experiments.

CROSS-REFERENCES

Lessons In Electric Circuits, Volume 1, chapter 1: "Basic Concepts of Electricity"

Lessons In Electric Circuits, Volume 1, chapter 8: "DC Metering Circuits"

LEARNING OBJECTIVES

How to measure voltage

Characteristics of voltage: existing between two points

Selection of proper meter range

ILLUSTRATION

INSTRUCTIONS

In all the experiments in this book, you will be using some sort of test equipment to measure aspects of electricity you cannot directly see, feel, hear, taste, or smell. Electricity-at least in small, safe quantities-is insensible by our human bodies. Your most fundamental "eyes" in the world of electricity and electronics will be a device called a multimeter. Multimeters indicate the presence of, and measure the quantity of, electrical properties such as voltage, current, and resistance. In this experiment, you will familiarize yourself with the measurement of voltage.

Voltage is the measure of electrical "push" ready to motivate electrons to move through a conductor. In scientific terms, it is the specific energy per unit charge, mathematically defined as joules per coulomb. It is analogous to pressure in a fluid system: the force that moves fluid through a pipe, and is measured in the unit of the Volt (V).

Your multimeter should come with some basic instructions. Read them well! If your multimeter is digital, it will require a small battery to operate. If it is analog, it does not need a battery to measure voltage.

Some digital multimeters are autoranging. An autoranging meter has only a few selector switch (dial) positions. Manual-ranging meters have several different selector positions for each basic quantity: several for voltage, several for current, and several for resistance. Autoranging is usually found on only the more expensive digital meters, and is to manual ranging as an automatic transmission is to a manual transmission in a car. An autoranging meter "shifts gears" automatically to find the best measurement range to display the particular quantity being measured.

Set your multimeter's selector switch to the highest-value "DC volt" position available. Autoranging multimeters may only have a single position for DC voltage, in which case you need to set the switch to that one position. Touch the red test probe to the positive (+) side of a battery, and the black test probe to the negative (-) side of the same battery. The meter should now provide you with some sort of indication. Reverse the test probe connections to the battery if the meter's indication is negative (on an analog meter, a negative value is indicated by the pointer deflecting left instead of right).

If your meter is a manual-range type, and the selector switch has been set to a high-range position, the indication will be small. Move the selector switch to the next lower DC voltage range setting and reconnect to the battery. The indication should be stronger now, as indicated by a greater deflection of the analog meter pointer ( needle), or more active digits on the digital meter display. For the best results, move the selector switch to the lowest-range setting that does not "over-range" the meter. An over-ranged analog meter is said to be "pegged," as the needle will be forced all the way to the right-hand side of the scale, past the full-range scale value. An over-ranged digital meter sometimes displays the letters "OL", or a series of dashed lines. This indication is manufacturer-specific.

What happens if you only touch one meter test probe to one end of a battery? How does the meter have to connect to the battery in order to provide an indication? What does this tell us about voltmeter use and the nature of voltage? Is there such a thing as voltage "at" a single point?

Be sure to measure more than one size of battery, and learn how to select the best voltage range on the multimeter to give you maximum indication without over-ranging.

Now switch your multimeter to the lowest DC voltage range available, and touch the meter's test probes to the terminals (wire leads) of the light-emitting diode (LED). An LED is designed to produce light when powered by a small amount of electricity, but LEDs also happen to generate DC voltage when exposed to light, somewhat like a solar cell. Point the LED toward a bright source of light with your multimeter connected to it, and note the meter's indication:

Batteries develop electrical voltage through chemical reactions. When a battery "dies," it has exhausted its original store of chemical "fuel." The LED, however, does not rely on an internal "fuel" to generate voltage; rather, it converts optical energy into electrical energy. So long as there is light to illuminate the LED, it will produce voltage.

Another source of voltage through energy conversion a generator. The small electric motor specified in the "Parts and Materials" list functions as an electrical generator if its shaft is turned by a mechanical force. Connect your voltmeter (your multimeter, set to the "volt" function) to the motor's terminals just as you connected it to the LED's terminals, and spin the shaft with your fingers. The meter should indicate voltage by means of needle deflection (analog) or numerical readout (digital).

If you find it difficult to maintain both meter test probes in connection with the motor's terminals while simultaneously spinning the shaft with your fingers, you may use alligator clip "jumper" wires like this:

Determine the relationship between voltage and generator shaft speed? Reverse the generator's direction of rotation and note the change in meter indication. When you reverse shaft rotation, you change the polarity of the voltage created by the generator. The voltmeter indicates polarity by direction of needle direction (analog) or sign of numerical indication (digital). When the red test lead is positive (+) and the black test lead negative (-), the meter will register voltage in the normal direction. If the applied voltage is of the reverse polarity (negative on red and positive on black), the meter will indicate "backwards."

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PARTS AND MATERIALS Multimeter, digital or analog Assorted batteries One light-emitting diode (Radio Shack catalog # 276-026 or equivalent) Small "hobby" motor, permanent-magnet type (Radio Shack catalog # 273-223 or equivalent) Two jumper wires with "alligator clip" ends (Radio Shack catalog # 278-1156, 278-1157, or equivalent) A multimeter is an electrical instrument capable of measuring voltage, current, and resistance.

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Physics - Introduction to Electric Current - What Happens When a Current Passes Through a Circuit?

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Electric Circuits:  Basics of the voltage and current laws.

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SELECT HTML5 SIMULATIONS
SELECT A SIMPLE ELECTRIC CIRCUIT ON THE LEFT SIDE PANE

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SIMPLE CIRCUITS

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For this lab you will be looking at the connections between voltage, current and resistance in a simple electrical circuit. Click on the multimeters to read the voltage or the current. Click on the resistor or battery pack to generate new random voltages or resistances.

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For this lab you will be looking at voltage and current in a series circuit. Click on the multimeters to read the voltage or the current. Click on the resistor or battery pack to generate new random voltages or resistances. Click on the move meter button to switch your meters to another resistor.

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For this lab you will be looking at voltage and current in a series circuit. Click on the multimeters to read the voltage or the current. Click on the resistor or battery pack to generate new random voltages or resistances. Click on the move meter button to switch your meters to another resistor.

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additional phet

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step 2
Electrons have a negative charge. Call it negative 1 electron volt. Neutrons are neutral. Protons have a plus 1 electron volt charge. So, what is a charge? Charge is the potential to attract or repel a charged particle

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Description: The video shows how to combine two dipoles in series, then in parallel.
Definition
In series: Refers to an assembly where the dipoles are placed one after the other and traversed by the same current.

In parallel: In a parallel circuit (multi-loop), there are several branches. The first branch, where the generator is located.

flash animation

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SERIES or PARALLEL CIRCUIT | an activity - Free flash animation for electricity learning - Interactive flash simulation to associate two dipoles (bulbs lamps) in series or parallel and see the difference between both. Be careful about short circuits - Physics and Chemistry by a Clear Learning in High School, Middle School, Upper School, Secondary School and Academy. PCCL

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Pedagogy : SERIES or PARALLEL CIRCUIT | an activity - Free flash animation for electricity learning - Interactive flash simulation to associate two dipoles (bulbs lamps) in series or parallel and see the difference between both. Be careful about short circuits. Physics and Chemistry by a Clear Learn…

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step 8

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Description: A simple circuit - Concept of a single loop circuit - The video allows you to discover the basic vocabulary such as battery, generator, banana plugs, crocodile clips, switch, terminal, connection wire ...

Definition
Electrical circuit: An electrical network is an interconnection of electrical components (e.g., batteries, resistors, inductors, capacitors, switches, transistors) or a model of such an interconnection, consisting of electrical elements (e.g., voltage sources, current sources, resistances, inductances, capacitances). An electrical circuit is a network consisting of a closed loop, giving a return path for the current.

flash animation

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Simple circuit - Loop - Electricity - SIMULATION | Interactive flash animation to learn vocabulary like connecting wires, interruptor or electrical switch, bulb, baterry... Physics. PCCL

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Simple circuit - Loop - Electricity - SIMULATION | Interactive flash animation to learn vocabulary like connecting wires, interruptor or electrical switch, bulb, baterry... Physics. PCCL

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step 8

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step 1

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Step 10:                  Static electricity

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Step 10:                  Static electricity