Tesla Coil: Difference between revisions

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== Age ==
{| class="wikitable" style="color:black; background-color:#ddd; margin-left: auto; float:right"
| [[Physics]], [[Engineering]]:
| Electricity, Circuits
|-
| Grade Range:
| [[Middle School]], [[High School]]
|-
| Format:
| [[Stage]]
|}


Elementary School, Middle School, High School
The Tesla Coil is one of our most impressive and awe-inspiring demonstrations. This demonstration will generate a large and powerful bolt for students to see, and it might generate some surprised screams as well!
 
== Format ==
 
Stage Show


== Materials ==
== Materials ==


    Tesla Coil
* Tesla Coil (Inner Coil, Outer Coil, Stand)
    Tesla wand (with copper ball on end and grounding wire)
* Grounding Rod
    Metal coil tip
* Metal Tip
    Transformer box
* Circuit Box with Outlet Cable
    Two green power cables to connect Tesla Coil to transformer box
* Power Cables (2 Green, 1 Red)
    Screwdriver
* Long Flathead Screwdriver
    Sandpaper
* Sandpaper
    Power strip with on/off switch
* Power Strip with On/Off Switch


== Safety Precautions ==
== Safety Precautions ==


Science Theatre demonstrators must keep the safety of themselves and their audience in mind at all times. All Science Theatre demonstrators must have read through the Safety Training page. The ST Safety Box with first aid kit, fire extinguisher, etc. should always be available to demonstrators. Always wear safety gloves, glasses, and a labcoat if handling chemicals; always perform potentially dangerous demonstrations at a safe distance from the audience; and always keep a very close eye on any volunteers you call from the audience. The Tesla Coil is harmless if used correctly, but can be EXTREMELY dangerous if misused! Only a trained volunteer should go near the Tesla Coil. Extreme caution should be exercised while the devise is turned on. Both the coil itself and the transformer box may carry very harmful levels of voltage. Beware that the Tesla coil will turn on as soon as it is plugged in - use a power strip with an on/off switch to help you control the power flow.
The Tesla Coil is safe if used correctly, but can be EXTREMELY dangerous if misused! Only a trained volunteer can be near or use the Tesla Coil. Extreme caution should be exercised while the device is turned on. Both the coil itself and the circuit box may carry harmful levels of voltage, so ground the Tesla Coil after every use. Follow the guidelines below in order to safely use the Tesla Coil:
* Use a power strip with an on/off switch. This will provide you with a safe way to turn the coil on and off.
* The Tesla Coil should not be turned on until all the cords are in place, the lid is on the circuit box, the grounding rod is plugged in and held near the tip, and the audience is at least six feet away.
* No one should touch or handle any part of the system, excluding the grounding rod and the screwdriver, while the power is on. Upon turning off the Tesla Coil, the grounding rod must be swept along opposite sides of the coils to remove any excess charge, as well as the tip.
* Do not perform this demonstration until you remove all metal objects and electronic devices from your person, such as necklaces, rings, bracelets, phones, keys and wallets.
* You must warn the audience that anyone with a pacemaker or metal implant should move away from the stage, and should be at least 15 feet away from this demonstration to prevent any risk of damage to their device.
* Please see the [[Demonstration Safety]] Page for additional General Safety Precautions, and read the Loud Demonstration Safety section.


    The device should not be turned on unless the plastic transformer box is closed.
    No one should ever touch the device while turned on except with the grounding wand.
    You must sweep the coil with the grounding wand after using the coil to eliminate all excess charge.
    Do not perform the Tesla coil near any metal or electronic devices - empty your pockets before the demonstration.
    You must warn the audience that anyone with a pacemaker or metal implant should move away from the stage.
== Preparation ==
Start off by hooking everything up. Connect the two green power cords to the coil itself and to the transformer box. Connect the black power cord attached to the grounding wand to one of the three grounding outlets on the transformer box. Make sure the plastic lid is screwed into the transformer box. Place the metal tip on top of the Tesla coil. Finally, plug the black power cord into the transformer box and into the power strip - make sure the power strip is turned off until you're ready for it (or simply leave it unplugged at first)!
There is a spark gap inside the transformer box that moderates the power output of the box (see diagram). You may need to sand down the metal tips on this gap to remove deposits that will inhibit the sparking. To do this, make sure the coil is unplugged and remove the transformer box's plastic lid. Then simply rub the ends of the metal on each side with some sandpaper.


== Demonstration ==
== Demonstration ==


First warn the audience that this demonstration will generate large electromagnetic fields that may be dangerous to anyone with a pacemaker or metal implant - anyone with such devices should move very far away for safety. Make sure EVERYONE in the audience is at least 15 ft away from the Tesla Coil no matter what.
Preparation: Place the small coil on the stand, aligning the black-spot leg with the black-spot hole. put the large coil inside of it and onto the stand, aligning the port at the bottom of it with the ports on the small coil. Place the metal tip on top of the coil. Plug the red power cable into the port on the large coil, and connect it to one of the three vertical grounding ports on the circuit box. Plug the green cables into the small coil, and connect them to the two horizontal ports on the circuit box. Plug the grounding rod into one of the three grounding ports. Open the circuit box, and check the spark gap to make sure it is clear of rust or buildup. If there is any, use the sandpaper to clean off the tips. Close the circuit box, and use the screwdriver to close the spark gap fully. Now, plug the power strip in, keeping the switch in the OFF position. Plug the outlet cable into the circuit box, and place the other end next to the power strip. DO NOT PLUG IT IN YET.
 
Start off by grounding the coil by placing the copper head of the grounding wand up against the coil tip. Then plug in and turn on the coil and you should see the spark gap in the transformer gap light up with a spark. Now you can move the wand away from the coil tip and you should see a spark bridge between them.
 
You can change the spark gap width during the demonstration. Making this gap smaller will make it easier to produce a spark on the coil, but will reduce the power of the spark. You may want to start off with this gap small so you can get a spark going, then increase the gap as much as you can to make the spark more dramatic. You can adjust the gap by inserting a flathead screwdriver in the hole in the transformer box and using it to turn the dial inside.
 
You can turn the coil on and off a few times if it's having trouble starting up - sometimes this will help to get it going. Usually, if it's not working, you just need to reduce the spark gap width.
 
== What to Say ==
 
We all grew up with electric lightbulbs, cell phones, computers, and tons of other electronic devices that we rely on evry day. Did you know that just a little more than a hundred years ago, none of these electronic devices existed? At the turn of the nineteenth century, a great inventor named Nikola Tesla was one of a handful of scientists working to unlock the secrets of electricity. Among the many things that he did, he wanted to build a device to generate huge voltages to help him study x-rays, radio, the alternating current, power transmission, and other phenomenon. We have here a Tesla Coil, very similar to the one Tesla himself invented, so we can show you what it means to generate a huge voltage.
 
How do you get a huge voltage? High voltages are created by a concentration of charges. Electrons are subatomic particles that carry charge - so if we can squeeze enough electrons together, we can produce a large voltage. The Tesla coil works by forcing as many electrons as it can into the very tip on the coil, so we get a huge concentration of charge and a huge voltage.
 
What does a huge voltage look like? What does it do? We can show you using the Tesla coil!
 
(Perform the demonstration)
 
So what did you guys see? You saw a spark jumping from the wand to the tip! An electrical spark is a conduction path that forms in the air - its sort of like a wire that forms spontaneously in the air, but instead of copper, this wire is made of superheated gas ions! The conduction path allows electrons to flow from the wand head to the tip.
 
Now, you don't normally see sparks in the air, do you? Even when there are small voltage differences, like those created by the wires in your house, you normally don't get sparks. The reason is that, while metal wires are conductors that make it easy for electrons to flow, the air is an insulator. The air resists the flow of electrons, so we normally don't see electrons flowing through it. If you get a sufficient voltage difference though (like the one between the high voltage metal tip and the 0-volt grounded wand), you get an electric field strong enough to force the electrons on the tip to travel over to the wand. The air is not conducting electricity - no longer insulating it! We call this effect dielectric breakdown. This produces a cascade of moving electrons, ionizes and superheats the air molecules in between, sets up that plasma conduction path, and produces the brilliant glowing spark that we see.
 
So it looks like this demonstration is all about electricity - but it also has a lot to do with magnetism as well. Have you ever wondered why a refrigerator or bar magnet is attracted to some metal objects? The magnet seems to be pulled towards that metal, even though there's nothing reaching out to grab it - the force is invisible. The phenomenon responsible for producing this force is a magnetic field. The Tesla coil relies on a huge magnetic field just like the one from the bar magnet, but much stronger. Take a closer look at the Tesla Coil - the metal tip is actually not in any way connected to the wall outlet, so how does all these electrons get transferred to the tip? Well, the power from the wall supplies the energy to set up a current (a flow of electrons) in the primary coil. The primary coil isn't attached to the secondary coil or the tip at all, but these moving electrons from the primary coil current create a large magnetic field right in the center of the device. When each turn of wire in the secondary coil is exposed to this magnetic field, it causes the electrons in that secondary wire to start flowing. So the current in the primary wire actually induces a current in the secondary wire by a magnetic field. Once the current is set up in the secondary coil, electrons start spiraling up the wire towards the tip and are forced together up there, producing the high voltage.
 
== Why It Is ==


The information in the "What to Say" section above should tell you all you need to know about the science behind this demonstration, but here are a few more details just for fun. The Tesla Coil is a very complicated instrument and you can find much more information online.
# Explain to the audience that you will be showing them the Tesla Coil, a device first invented by Nikola Tesla. Alert the audience that it will be a loud demonstration, and that any individuals with implanted devices should stay at least 15 feet away for this presentation.
# Explain to the audience the different parts of the circuit: Transformer, Capacitor, Coils, Spark Gap. you can use the coils as an example of a transformer. State that the spark gap is the limiting factor in this system; If the spark gap stays small, the bolt will stay small, and if it gets bigger, the bolt will as well!
# Put on safety glasses and pick up the grounding rod. Explain the purpose of the grounding rod.
# Have your co-presenter sit next to the circuit box, away from the coil and within reach of the power strip. explain that they will be controlling the spark gap, and therefore the size of the bolt. Have them plug in the circuit box to the power strip while still in the OFF position.
# When ready, hold the ball on the end of the grounding rod against the tip of the Tesla Coil. Give your co-presenter the OK, and after a brief countdown have them turn on the coil.
#* When first turned on, there will be a small spark or no visible spark, depending on how open the spark gap is. Have your co-presenter open up the spark gap with the screwdriver slowly, allowing the bolt to gradually grow larger and larger. As this happens, slowly move the grounding rod further from the coil, so the audience can see how big the bolt is getting.
#* When the bolt starts to get bigger than 6in, do not let the cord of the grounding rod be closer to the coil than the ball on the end. The discharge from the coil is powerful enough to forgo the insulation of the wire. DO NOT TOUCH THIS WIRE, OR ANY OTHER PART OF THE COIL, WHILE IT IS ON.
#* At some point, the spark gap will get too big and the tips will get too oxidized, and the power will cut out. Have your co-presenter slowly close the spark gap. It will jump across again, but the longer it runs the more corroded the tips will get. Have them slowly close up the gap.
#* Once they close the gap, turn off the power. Ground the coil, and have them unplug it from the power strip.
# After presenting, ask the audience the following questions:
## What color was the bolt? (Blue/Purple) What causes the color of the bolt? (Oxygen)
## What state of matter was the bolt? (Plasma)
## Can anyone smell the odor coming from the demo? If so, what is that odor? (Ozone)


The magnetic field interaction between the primary and secondary coils is a phenomenon called induction, the same concept at play in a transformer. A huge current is sent through the primary coil, which has only a few turns of wire. This induces a huge voltage (but lesser current) in the secondary coil, which has many, many turns of wire. A Tesla coil differs from a traditional iron-core transformer in that the details of the alternating current at work in its design produce an even greater stepped-up voltage than in the traditional transformer - the stepped up voltage will go as the square of the ratio of turns rather than the ratio itself.
== Why This Works ==


What is the voltage produced by the Tesla Coil? You can get an idea based on how long a spark you can produce. The dielectric strength of air is about 3 million volts per meter. In other words, it takes about 30,000 Volts for each centimeter's worth of spark that you are able to produce. Of course, a current will only flow when a voltage difference exists, so we introduce the grounded wand (fixed at 0 Volts by definition) to provide a lower potential for the electrons to "fall" into. So, if you have a spark that will extend to at most 2 cm, you can estimate that the metal tip is at 60,000 V and the grounded wand is at 0 V.
The Tesla Coil was invented by Nikola Tesla, a scientist in the late 19th and early 20th centuries. The device is a way to see how a charge can be built up and made larger by use of what we call ''Transformers''. A transformer is pretty simple overall: You set up two coils, with one inside the other, like the Tesla Coil. Then, you run a charge through one of the coils. The size of the coils affect the outcome you get; That is, if one coil is bigger than the other, then you will get a ''different charge'' out of the second coil. In this case, we run a charge through the smaller coil, which means the larger one will generate a larger charge. This is known as a ''Step-up Transformer'', since we are "stepping up" the voltage. Likewise, if we ran the charge through the big coil instead, the small coil would give a smaller charge, resulting in a ''Step-down Transformer''.  


Note that there are also a variety of alternating current concepts at work in the Tesla Coil, although we have not emphasized them here.
In our circuit, we start with the voltage from a wall outlet and send it through a step-up transformer, which boosts the voltage by a factor of 50. It then sends the charge to the capacitors in the circuit. ''Capacitors'' are, simply put, a set of metal plates that are really close to each other, with only a tiny amount of space between them. These gaps will hold a charge, making a capacitor something similar to a battery. Unlike a battery, a capacitor doesn't slowly discharge; it empties ''all the charge it has at once'', which gives a boost to the voltage by a factor of 10. From here, the circuit goes into our Tesla coil's outer, smaller coil, which acts like a second step-up transformer, which boosts the voltage by a factor of 100. In the end, the entire system will take in the wall voltage and can multiply it by as much as 50,000!


== Real Life Examples ==
The output of the system is controlled by what is called a ''Spark Gap''. The spark gap is our adjustable resistance for the system, and controls how big the bolt can get. If we leave it closed, the bolt cannot get big, and might not even be visible. As we widen the spark gap, the bolt will grow bigger, with a ratio of about 10:1. That is, for every inch the spark gap opens, the bolt can fire an extra 10 inches! The maximum possible output of the system is controlled by the spark gap, which greatly limits the actual output of the system. Since it is open to the air, the copper tips of the spark gap quickly oxidize while the Tesla coil is running. This rapid oxidation makes it harder for the spark gap to conduct, and needs to be removed between runs to allow the coil to run.


The spark produced by the Tesla coil operates on the same principal as lightning - dielectric breakdown.
When we see the bolt, we are actually looking at ''Plasma'', the fourth state of matter. We don't often encounter plasma in our day-to-day lives, but it is the most common state of matter in our universe! Plasma is when you excite a gas so much that it gets super hot, and the electrons start flying around it really fast, no longer staying with their original atoms or molecules. The color of the bolt, the blue-purple color, is because of the gas in the air being so excited. Notably, it is oxygen gas, since nitrogen gives off a white light when excited. Oxygen gives off a blue-purple color when it is excited. This is a different reason for why the sky is blue, however, since our sky and air is all gases, and not made of plasma! Lastly, the smell you might notice is a result of this oxygen plasma. When the oxygen atoms got all excited, some of them split and recombine not as O<sub>2</sub>, the oxygen we breathe, but as O<sub>3</sub>, which is known as ''ozone''.


Modified version of the Tesla coil have been put to use to generate high voltages for radio transmission, x-ray generators, fluorescent devices, and a variety of other applications.
== Tips and Tricks ==


The principles of electronics that the Tesla coil illustrates - current, voltages, induction - are the foundation of all the modern electronic devices that you use every day!
<!--* The spark produced by the Tesla coil operates on the same principal as lightning - dielectric breakdown. -->
* Modified versions of the Tesla coil have been put to use to generate high voltages for radio transmission, x-ray generators, fluorescent devices, and a variety of other applications.
* The Tesla Coil is a part of the [[Quantum Mechanics Show]] and the [[Electromagnetism Show]].

Latest revision as of 16:12, 26 August 2016

Physics, Engineering: Electricity, Circuits
Grade Range: Middle School, High School
Format: Stage

The Tesla Coil is one of our most impressive and awe-inspiring demonstrations. This demonstration will generate a large and powerful bolt for students to see, and it might generate some surprised screams as well!

Materials

  • Tesla Coil (Inner Coil, Outer Coil, Stand)
  • Grounding Rod
  • Metal Tip
  • Circuit Box with Outlet Cable
  • Power Cables (2 Green, 1 Red)
  • Long Flathead Screwdriver
  • Sandpaper
  • Power Strip with On/Off Switch

Safety Precautions

The Tesla Coil is safe if used correctly, but can be EXTREMELY dangerous if misused! Only a trained volunteer can be near or use the Tesla Coil. Extreme caution should be exercised while the device is turned on. Both the coil itself and the circuit box may carry harmful levels of voltage, so ground the Tesla Coil after every use. Follow the guidelines below in order to safely use the Tesla Coil:

  • Use a power strip with an on/off switch. This will provide you with a safe way to turn the coil on and off.
  • The Tesla Coil should not be turned on until all the cords are in place, the lid is on the circuit box, the grounding rod is plugged in and held near the tip, and the audience is at least six feet away.
  • No one should touch or handle any part of the system, excluding the grounding rod and the screwdriver, while the power is on. Upon turning off the Tesla Coil, the grounding rod must be swept along opposite sides of the coils to remove any excess charge, as well as the tip.
  • Do not perform this demonstration until you remove all metal objects and electronic devices from your person, such as necklaces, rings, bracelets, phones, keys and wallets.
  • You must warn the audience that anyone with a pacemaker or metal implant should move away from the stage, and should be at least 15 feet away from this demonstration to prevent any risk of damage to their device.
  • Please see the Demonstration Safety Page for additional General Safety Precautions, and read the Loud Demonstration Safety section.


Demonstration

Preparation: Place the small coil on the stand, aligning the black-spot leg with the black-spot hole. put the large coil inside of it and onto the stand, aligning the port at the bottom of it with the ports on the small coil. Place the metal tip on top of the coil. Plug the red power cable into the port on the large coil, and connect it to one of the three vertical grounding ports on the circuit box. Plug the green cables into the small coil, and connect them to the two horizontal ports on the circuit box. Plug the grounding rod into one of the three grounding ports. Open the circuit box, and check the spark gap to make sure it is clear of rust or buildup. If there is any, use the sandpaper to clean off the tips. Close the circuit box, and use the screwdriver to close the spark gap fully. Now, plug the power strip in, keeping the switch in the OFF position. Plug the outlet cable into the circuit box, and place the other end next to the power strip. DO NOT PLUG IT IN YET.

  1. Explain to the audience that you will be showing them the Tesla Coil, a device first invented by Nikola Tesla. Alert the audience that it will be a loud demonstration, and that any individuals with implanted devices should stay at least 15 feet away for this presentation.
  2. Explain to the audience the different parts of the circuit: Transformer, Capacitor, Coils, Spark Gap. you can use the coils as an example of a transformer. State that the spark gap is the limiting factor in this system; If the spark gap stays small, the bolt will stay small, and if it gets bigger, the bolt will as well!
  3. Put on safety glasses and pick up the grounding rod. Explain the purpose of the grounding rod.
  4. Have your co-presenter sit next to the circuit box, away from the coil and within reach of the power strip. explain that they will be controlling the spark gap, and therefore the size of the bolt. Have them plug in the circuit box to the power strip while still in the OFF position.
  5. When ready, hold the ball on the end of the grounding rod against the tip of the Tesla Coil. Give your co-presenter the OK, and after a brief countdown have them turn on the coil.
    • When first turned on, there will be a small spark or no visible spark, depending on how open the spark gap is. Have your co-presenter open up the spark gap with the screwdriver slowly, allowing the bolt to gradually grow larger and larger. As this happens, slowly move the grounding rod further from the coil, so the audience can see how big the bolt is getting.
    • When the bolt starts to get bigger than 6in, do not let the cord of the grounding rod be closer to the coil than the ball on the end. The discharge from the coil is powerful enough to forgo the insulation of the wire. DO NOT TOUCH THIS WIRE, OR ANY OTHER PART OF THE COIL, WHILE IT IS ON.
    • At some point, the spark gap will get too big and the tips will get too oxidized, and the power will cut out. Have your co-presenter slowly close the spark gap. It will jump across again, but the longer it runs the more corroded the tips will get. Have them slowly close up the gap.
    • Once they close the gap, turn off the power. Ground the coil, and have them unplug it from the power strip.
  6. After presenting, ask the audience the following questions:
    1. What color was the bolt? (Blue/Purple) What causes the color of the bolt? (Oxygen)
    2. What state of matter was the bolt? (Plasma)
    3. Can anyone smell the odor coming from the demo? If so, what is that odor? (Ozone)

Why This Works

The Tesla Coil was invented by Nikola Tesla, a scientist in the late 19th and early 20th centuries. The device is a way to see how a charge can be built up and made larger by use of what we call Transformers. A transformer is pretty simple overall: You set up two coils, with one inside the other, like the Tesla Coil. Then, you run a charge through one of the coils. The size of the coils affect the outcome you get; That is, if one coil is bigger than the other, then you will get a different charge out of the second coil. In this case, we run a charge through the smaller coil, which means the larger one will generate a larger charge. This is known as a Step-up Transformer, since we are "stepping up" the voltage. Likewise, if we ran the charge through the big coil instead, the small coil would give a smaller charge, resulting in a Step-down Transformer.

In our circuit, we start with the voltage from a wall outlet and send it through a step-up transformer, which boosts the voltage by a factor of 50. It then sends the charge to the capacitors in the circuit. Capacitors are, simply put, a set of metal plates that are really close to each other, with only a tiny amount of space between them. These gaps will hold a charge, making a capacitor something similar to a battery. Unlike a battery, a capacitor doesn't slowly discharge; it empties all the charge it has at once, which gives a boost to the voltage by a factor of 10. From here, the circuit goes into our Tesla coil's outer, smaller coil, which acts like a second step-up transformer, which boosts the voltage by a factor of 100. In the end, the entire system will take in the wall voltage and can multiply it by as much as 50,000!

The output of the system is controlled by what is called a Spark Gap. The spark gap is our adjustable resistance for the system, and controls how big the bolt can get. If we leave it closed, the bolt cannot get big, and might not even be visible. As we widen the spark gap, the bolt will grow bigger, with a ratio of about 10:1. That is, for every inch the spark gap opens, the bolt can fire an extra 10 inches! The maximum possible output of the system is controlled by the spark gap, which greatly limits the actual output of the system. Since it is open to the air, the copper tips of the spark gap quickly oxidize while the Tesla coil is running. This rapid oxidation makes it harder for the spark gap to conduct, and needs to be removed between runs to allow the coil to run.

When we see the bolt, we are actually looking at Plasma, the fourth state of matter. We don't often encounter plasma in our day-to-day lives, but it is the most common state of matter in our universe! Plasma is when you excite a gas so much that it gets super hot, and the electrons start flying around it really fast, no longer staying with their original atoms or molecules. The color of the bolt, the blue-purple color, is because of the gas in the air being so excited. Notably, it is oxygen gas, since nitrogen gives off a white light when excited. Oxygen gives off a blue-purple color when it is excited. This is a different reason for why the sky is blue, however, since our sky and air is all gases, and not made of plasma! Lastly, the smell you might notice is a result of this oxygen plasma. When the oxygen atoms got all excited, some of them split and recombine not as O2, the oxygen we breathe, but as O3, which is known as ozone.

Tips and Tricks

  • Modified versions of the Tesla coil have been put to use to generate high voltages for radio transmission, x-ray generators, fluorescent devices, and a variety of other applications.
  • The Tesla Coil is a part of the Quantum Mechanics Show and the Electromagnetism Show.
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