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Our eyes can see many of these waves, but not all! For example, the shortest waves that we can see are purple light. The purple color with the shortest wave is violet. Waves that are a little bit shorter create “ultra-violet” waves. These waves are too close together for our eyes to see. The Sun creates radiant energy, which includes ultra-violet waves, and many other invisible waves. Have you ever been sunburned? You can blame the ultra-violet light waves!

Waves shorter than ultra-violet waves can fit into small places. That is why they are used for X-rays. They are also created by nuclear power plants. Nuclear power plants use reactions between the smallest particles of matter to create a HUGE amount of energy. Because these particles are so small, their electromagnetic waves are even smaller than X-rays.

Red is the visible light wave with the longest waves. Waves that are a little bit longer are called infrared waves. Your remote control uses infrared waves to communicate with your TV. Scientists found that heat sources send out infrared waves, too. Guess what? You are a heat source, and you send out infrared waves! By measuring infrared waves, we can know how hot something is.

Waves longer than infrared waves are useful for running cell phones, radios, and satellites.

Waves shorter than ultra-violet waves are useful for investigating small things. Each wavelength has its own special uses!

But, how fast are these waves?
You know that the speed of light is super fast. It’s actually 670,616,629 miles per hour! All electromagnetic waves travel at the same speed. Remember, light is an electromagnetic wave. All electromagnetic waves travel at the speed of light! So, a radio tower and an X-ray machine create waves that travel at 670,616,629 miles per hour!

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This reading is about the relationship between electromagnetic waves, light and color.

Electromagnetic waves create one of the most important forms of energy for a human’s survival, light! You might be wondering, what does light have to do with electricity? Or even color? Read on to learn more about light. Electromagnetic waves create one of the most important forms of energy for human survival, light!  Light is actually an electromagnetic wave. This wave is made out of a photon. A tiny particle that moves through space. This means that light is a form of energy. If you have ever felt the sunlight on a summer day, you already know that energy from light can make heat! 

So, now that we have a basic understanding of how electricity is related to light…Have you ever thought about how your favorite colors are created? What makes a color blue? Or yellow? When we look at an object, we are really seeing reflected light. When we see a grumpy cat, the photons of light are reflected off the grumpy cat and into our eyes. When waves of light hit an object, some waves are absorbed by the object and some are reflected. 

The reflected waves are what you see.  Different wavelengths of reflected light create different colors! For example, when you see your favorite red shirt, the shirt is absorbing all the colors of light except for the color red. The frequency of light that we see as red is being reflected, and we see that shirt as red. 

The only colors that are different are white and black. White is a combination of all colors, so when we see white, the object is reflecting all the colors of light the same. Black is the opposite. When we see a black object that means almost all the colors of light are being absorbed. When you look at a black poster, the poster is absorbing all types of light. And, when you wear white shorts, they are reflecting all the light waves (but still get grass stains!).

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In the 1800s scientist began to better understand how electricity and magnetism were connected. At this time, travelers used a compass which pointed to the north pole. Scientists began to see that their electrical circuits would change where a compass pointed. A surprising discovery! This observation was important but it did not show the theory that connected electricity and magnetism.

Electricity flowing through a wire creates magnetic fields. These fields can attract other objects. As electricity flowed, then the wire would become magnetic. These magnetic fields may be hard to imagine, but if you let metal settle over time you can see the fields. The experiment described below shows the fields created by a rare earth magnet.

Now, scientist talk about electricity and magnetism together, so they study “electromagnetism.” You have been studying electromagnetism this whole time!

Electromagnetism is the big idea behind observations about electric currents and magnetic forces. A changing electric field creates magnetism. And, changing magnetic fields will create an electric field. These fields move creating waves of electromagnetism. It’s impossible to separate electricity from magnetism!

Waves of energy have very different sizes!

Electromagnetic waves are different than ocean waves or sound waves. Waves that you can see and hear need to move water or air to travel. These waves need to be in something. Electromagnetic waves can be anywhere, even space (which is big and empty)! These waves have a photon. There is no matter in a photon, just energy. These little packets of energy move in waves across the universe, and even across your eyeball right now!

These waves can be as small as 1 millionth of a millimeter (0.0000000001 millimeters!). We use small waves like these to take X-rays. Other waves can be 100 meters long. We use long waves like these to send AM radio over long distances. Your FM radio uses waves that are between 1 and 10 meters long. The length of a wave makes it useful for different things.

Radios are a good example of how electricity and magnetism are examples of electromagnetic waves. The radio waves are electromagnetic waves. These waves are created by electricity flowing into a transmitter antenna which makes electrons vibrate up and down it, producing radio waves. Then, the radio waves move electrons in your radio’s antenna. (Yes, your car has a radio antenna, even if you can’t see it!). Your radio uses these moving electrons to understand the sounds sent by the radio tower. This is how your radio creates music!

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Tesla’s makes an electric car called the Model S. This car works because of its incredible battery. Tesla’s battery pack is made of thousands of little batteries. Each little battery is filled with lithium ions. So, the designers say the battery pack is full of thousands of lithium ion cells. Lithium ion cells are also used to power your laptop for hours and hours. These types of batteries are extremely powerful because the chemicals inside can store a lot of electricity.

The battery’s power depends on the number of cells, so a Tesla’s battery weighs over one thousand pounds (a laptop weighs slightly less!). The batteries also come with a heating system, so Tesla car owners can start their car during cold weather.

Just like a cell phone runs out of battery, a car could run out of battery if it is not recharged. A Tesla’s battery pack is recharged by electricity. It’s easy to recharge the battery. There are charging stations at rest stops and malls, and it’s easy to put one in your home too! So neat!

The electricity from the battery is used to power a small motor, which is the size of a watermelon. This tiny, mighty engine converts electrical energy into mechanical work!

The induction motor uses alternating currents (A.C.) of electricity. However, we know batteries supply direct current (D.C.) power. That means engineers need to convert D.C. into A.C.. These engineers used a component called an inverter. The D.C. is always flowing. So, an inverter simply changes which side of the circuit receives the initial flow of electrons. This way the motor gets electricity from one direction, and then the other. It alternates which direction the power comes from so it creates A.C. power.

The A.C. induction motor uses this electricity to produce a magnetic field, causing the rotator inside the engine to move. The rotator is connected to gears. The rotator and the gears rotate in the same direction. The gears are attached to the tires by an axle. The car speeds up when more electricity is sent to the motor which causes the rotator to spin faster which makes the tires rotate faster. So the speed of a Tesla is controlled by the software sending electricity to the A.C. induction motor.  All these parts allow this electric car to go from stopped to 60 miles per hour in just 3.2 seconds! Count one, two, three, could you imagine going 60 miles per hour already?

Citizen Scientists
You may know that cell phone batteries hold less charge as they get older. All batteries become less effective as they are used. Tesla owners were curious. Do their Model S batteries get much worse over time? In 2017, Tesla owners across the world added data to a Google Sheet about their battery. This data is “crowdsourced”, which means lots of people added little bits of data. Crowdsourced data is not as good as scientifically discovered data, but it is useful in this case. Tesla drivers almost all reported that their battery was more than 90% effective. Even drivers that charged their car over 500 times!

https://www.teslarati.com/how-long-will-tesla-battery-last-degradation/

So, there’s plenty of other electric cars out there, why focus on the Tesla brand? Tesla employees works hard every day to make these cars better and better looking. These cars are fast and look great. So many people want one that you have to order it and then wait for it. People are attracted to buying cars that look nice, are super fast, popular, and help out the planet, too! However, this does not mean there are no other electric car companies! Companies like: BMW, Nissan, Chevrolet, Kia are all successfully building electric cars for families like yours!

One vision, Many inventions
The Tesla Company invents sustainable, electrical solutions for more than just cars! Tesla also sells solar panels and solar roofs that help people create their own energy using the Sun. Their solar roofing tiles are guaranteed for as long as your house is standing “or infinity, whichever comes first.” A guarantee means they promise it will work or they will come fix it. Most roofs are guaranteed for less than 10 years. Tesla guarantees them forever!
If you want to learn more, you can go to their website:

tesla.com/solarroof

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Who doesn’t love a summer road trip to the beach? Well, being jam packed in a car being forced to listen to your parent’s boring music, is a bit annoying. But, there is another reason why you should feel annoyed! Almost all these cars you see burn large amounts of gas which creates pollution. Pollution is chemicals and waste humans create and add to the water or air!

Um, say what?

Most cars use fossil fuels to power the engine. Fossil fuels have energy from dead plants and animals that were alive millions of years ago. When people burn fossil fuels to power vehicles, they release chemicals that are harmful to the planet. For example, when a car drives past you, you see a trail of smoke. The fire from burning fossil fuels in the engine creates this smoke. These chemicals from one car will not hurt you. But, there are over 1,000,000,000 cars today! That’s more than a billion!

This problem led many people to think about ways on how we can design cars to produce much less pollution. This is where electric cars come in! Over the last decade or so, electric cars have become very popular. Perhaps it is the design and the sleek interior that have people amazed. Or, the lack of pollution might be the big attraction. Either way, electric cars are incredibly fast, reliable, and “earth-friendly”. People use “earth-friendly” to describe things that produce very little or no pollution. So, what’s the story about these electric cars? Fasten your seatbelts, and we will *drive* right in with the next chapter!

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Nikola Tesla was another outstanding physicist and scientist. He was “ahead of his time” because he saw things that would happen later.

Did you know Tesla was one of Thomas Edison’s close employees? In fact, many scientists argue Tesla had better ideas than Thomas Edison. How can this be? Let’s dive deeper into Tesla’s past and his groundbreaking inventions. In the end, you can decide for yourself, who had the bigger impact on how we use electricity.

Nikola Tesla was born in Smiljan, Croatia in 1856. Croatia is a small Eastern Europe country that borders the Adriatic Sea, which is part of the massive Mediterranean Sea. Like Edison, Tesla was intelligent in school and questioned everything. He did so well in math tests that teachers accused him of cheating!

Tesla studied Math and Physics at the University of Prague. He worked extremely hard. He studied from 3 am to 11 pm every day. He never took off during the weekend or even on holidays. That’s dedication! In 1884, Tesla immigrated from Croatia to New York. He was hired as an engineer for Thomas Edison.

Edison vs. Tesla

Edison and his employees were extremely impressed with Tesla’s hard work and what he learned in Croatia. One day, Edison said he would give Tesla $50,000 if he could improve the designs for one of his electric generators. Tesla immediately went to work. Later, Tesla showed Edison his solution for a new DC generator. Edison didn’t think Tesla would take him seriously and made fun of him. It was all a joke to Edison! This made Tesla very upset and he quit working for Edison soon after. 

Tesla opened his own company called the Tesla Electric Company. He opened his own laboratory in New York, and created an alternating current motor. “Alternating” means taking turns or switching directions. Before now, we have been discussing direct current because it flows in one direction. The electrons are pushed by a force called voltage. Now, we are discussing alternating currents which switch directions. Important note: electrons must always be moving to produce an electrical current.

Which one is better, you might ask? Running a city on AC is cheaper than DC. And, it is easier to make devices that use AC. So, power plants create alternating currents instead of Edison’s favorite direct currents. Things that run on batteries use direct current. So, a laptop uses DC power, and charges the battery with AC power. Tesla’s motor uses alternating current in to make the motor turn A ring of magnets called the stator creates a magnetic field. The magnets are created by putting electricity through metals in a specific way. This makes the inside spin, which rotates gears that rotate the tires. Magnets created by electricity power the car! See experiment 3 for a demonstration.

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Thomas Edison’s light bulbs are the simplest types of light bulbs. They have 3 basic parts: a glass globe, a filament, and a screw base. These light bulbs are called incandescent light bulbs because “incandescent” means creating light by being heated.

The glass globe, filament, and screw base combine to create an incandescent light bulb. The glass globe wraps all the parts of the bulb and provides a covering so that nothing can catch fire from the heat from the filament. A gas is put inside the glass globe that helps the filament create light for a long time.

The filament is the small metal coil that at the center of the bulb. The filament uses the electrical current to create light. The filament is made to resist the flow of electricity. As it begins to heat up, the filament creates light.

The incandescent light bulb was becoming popular, but Thomas Edison wanted to make it better and more efficient. So, Edison invented a carbon filament lamp by putting carbon on a piece of thread. This metal covered thread was called a filament. This created a light bulb that would be able to provide light for 13 hours. Eventually, Edison used threads from bamboo to create a stronger light bulb. It could illuminate up to a couple hundred hours! (Today, light bulbs can last thousands of hours!!)

The base’s most important job is to connect the electrical current to the light bulb. The base also protects the parts of the bulb, like the contact wires. These contact wires cannot be damaged because they allow a constant flow of electricity to the filament of the bulb.  

Chapter 1. Introduction. We include this fun (but silly) example of electricity from PhET.

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Close your eyes. Imagine being sent to a world with no electronics (yes, that includes no video games!), no cars, no microwave, and the only lights in your house came from small candles. You may think, there’s no way a world like this could have existed. But, it did!

You may have heard the name “Thomas Edison” many, many times. There’s a reason why he is mentioned often. Edison was one of the greatest American inventors. He invented the phonograph (something that played music), and the first motion picture machine. However, many people argue that his greatest contribution was perfecting the light bulb. Edison’s work allowed more people to work at nighttime, stay awake longer, and read more.

WHY INVENT THE LIGHTBULB?

Remember when you closed your eyes and imagined a world without electricity? It felt strange, right? Perhaps, even scary? Before the light bulb many people were scared of the dark as well. After the light bulb was perfected in 1879, people felt safer at night. Before the light bulb, people used candles or lanterns for light at night. Candles are incredibly dangerous because they easily start fires. 

Scientists thought electricity could solve this problem. Electricity creates sparks. And, when certain conductors get hot, they also create light. Electricity does not involve a flame. It seemed like a natural fit. But, using electricity to create light was difficult! Who could solve this problem?

PERFECTING THE LIGHTBULB

Thomas Edison was very active and learned a lot as a child. He also questioned everything around him. He drove his school teachers nuts! As an adult, he became interested in electricity, and eventually started his own company in 1878. He called it the Edison Electric Light Company. Despite what some people think, Thomas Edison did NOT actually invent the light bulb. In fact, 23 light bulbs were invented before Edison made his. BUT, he was the first to create a light bulb that would be sold to most Americans. To learn more about this light bulb, check out chapter 6!

JOSEPH SWAN WHO?

Ok…So, if Thomas Edison did not create the first light bulb, who did?

A scientist named Joseph Swan invented the light bulb in 1878. Swan patented his light bulb in England (a patent stops other people from stealing an inventor’s idea). Swan used a carbon rod in his light bulb. The carbon resisted electricity. When the carbon resisted electricity heat and light was released.

Swan started his own company of light bulbs. Swan’s light bulb produced light, but did not last very long. Carbon was also dirty so it made the inside of the light bulb dirty which trapped the light. Carbon rods were not the solution, but it was a good start.

Without Thomas Edison perfecting the light bulb, we may not be able to experience electricity the way we do today. Because Edison changed the light bulb so it would be commercially successful, reliable, and practical, he is given credit for perfecting the light bulb. 

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If you want to read more, look at the Smithsonian Magazine’s article “Lamp inventors 1880-1940: Carbon Filament Incandescent”

https://americanhistory.si.edu/lighting/bios/swan.htm

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Sooo…did Benjamin Franklin discover electricity? 

No! Benjamin Franklin added many ideas and theories about electricity. But, he did NOT discover it. However, this experiment with the kite proved that lightning is electrical in nature! That might not sound like a big deal, but back then, this discovery was a huge breakthrough in science. 

Lightning was a big problem, and is still a big problem today! It’s dangerous to be outside when lightning is nearby. Houses and buildings can get struck by lightning. Most buildings in Philadelphia at this time were made of wood so they would catch on fire. Lightning made life very dangerous at this time.

Franklin’s experiment showed how electrons from lightning storms can be moved over a conductor. In his experiment, the conductor was the hemp cord. He wanted to use this knowledge to protect people. He thought he could move lightning safely. He planned to put a hemp cord from the top of a building into the ground. Franklin named this device the lightning rod.  Lightning rods attract electricity and then a cord or wire moves the electricity away safely into the ground.  This means that houses can remain undamaged and safe during lightning storms and prevent outbreaks of deadly fires.  Ben Franklin’s lightning rod captures the lightning strikes near the top of someone’s house, and then the electrical current enters the rod. The rod is connected to the ground without touching the house. So, the lightning moves safely away from the house and into the ground. The house is protected from lightning! Genius idea, isn’t it?

In summary, Benjamin Franklin was smart, creative and worked hard. He studied the dangers of electricity to help his community. He used extra protection while carrying out his experiment. He took shelter in a dry cabin and kept the strings at the end of the kite dry. Kites should never be flown in thunderstorms now that we understand these dangers! We can thank Benjamin Franklin for risking his life and establishing the connection between lightning and electricity. Without his important discovery, there would be no such things as television, phones, electric lighting in homes, heaters, and just about anything electrical!

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Want to go back in time? Here is Ben Franklin’s article in the Pennsylvania Gazette describing the experiment investigating “Electric Fire”!

“As soon as any of the Thunder Clouds come over the Kite, the pointed Wire will draw the Electric Fire from them, and the Kite, with all the Twine, will be electrified, and the loose Filaments of the Twine will stand out every Way, and be attracted by an approaching Finger. And when the Rain has wet the Kite and Twine, so that it can conduct the Electric Fire freely, you will find it stream out plentifully from the Key on the Approach of your Knuckle. At this Key the Phial may be charg’d; and from Electric Fire thus obtain’d, Spirits may be kindled, and all the other Electric Experiments be perform’d, which are usually done by the Help of a rubbed Glass Globe or Tube; and thereby the Sameness of the Electric Matter with that of Lightning compleatly demonstrated.”

From the Franklin Institute’s records: https://www.fi.edu/benjamin-franklin/kite-key-experiment