Tag Archives: Electromagnetism

Can you change the color of oudin coil sparks?

An Oudin coil can take the energy out of your outlet and create sparks you can see! It’s sometimes called a mini tesla coil. The sparks on them usually look violet.

Oudin Coil spark

If you know the visible light spectrum, you might know that violet light is the most energetic color of light. 

Oudin Coil light

The oudin coil looks like it’s putting out a lot of energy, but there’s a different reason for the violet sparks. In fact, the color of the sparks don’t always have to be violet like most people see. To demonstrate, check out the oudin coil when it sparks in something else, like carbon dioxide. An easy way to get a bunch of carbon dioxide in one place is with its solid form — dry ice!


When surrounded by CO2, the sparks from this oudin coil are clearly a different color!

Oudin Coil ice sparks

The reason for the color shift is because of what is surrounding the oudin coil. Our air is less than 1% carbon dioxide. When sparking in air, the coil surrounded mostly by different gases (mainly nitrogen and oxygen). The answer to why that makes a difference is the same answer as to why different gases glow different colors when you put a lot of energy into them. 


light colors

If you split apart this light, with something like diffraction glasses, you’ll see each type of gas has a unique spectrum of light. The study and use of this phenomenon is called spectroscopy.

Lights and glasses

Spectroscopy is a way of identifying gases, and it’s how we know what far away things like stars are made out of! On a tiny molecular scale, CO2 and what makes up our air are fundamentally different, and will create differences we can see… if we are clever enough to notice. By playing with this oudin coil and looking at colors, we’re revealing secrets about a seemingly invisible world.

Written By: Amanda Williams


Microwave Plasma

We go through our daily lives encountering three of the states of matter; solid, liquid, and gas; nearly every moment, but the fourth, plasma, is much rarer for most of us. Plasma can be found around most forms of visible electricity, like lightning, but you can find it inside your microwave if you follow the steps below. Before you get started, however, this experiment MUST be carried out with immense care and with an adult present; it is very easy to get this experiment wrong and deal damage to not only your microwave, but yourself as well.

For this experiment, you’ll need a microwave, a toothpick, a microwave-safe glass container, three discs of cork (or any material you can stick a toothpick into and use to prop up the glass, and a match. Place the four discs of cork in the microwave so that one is in the center and the other three are around it far enough for the glass container can rest on top of them. This is essential, as air needs to flow between the inside of the glass container and the inside of the microwave. Stick the toothpick into the center cork disc, and set the microwave to 20 seconds, but don’t run it yet.

microwave plasma

Light the toothpick and cover with the glass container, closing the door of the microwave and hitting start. You should see arcs of plasma coming from the lit toothpick and while it’s tempting to leave it go and watch for a while, only let it run for a few seconds. Otherwise, the glass will get too hot and could shatter, spreading broken glass through your microwave and removing the housing for the plasma, potentially lighting your microwave on fire. After you’ve shut off your microwave, let it sit closed for about a minute, allowing the glass to cool down, otherwise the sudden inrush of cool air from the outside could shatter the still hot glass.

microwave plasma 1

Those plasma arcs were cool, but how exactly did we make them? Well, plasma is essentially ionized gas, requiring either an increase in heat or adding more electromagnetic force, both of which are happening inside the microwave. When an object is burned, the fire is actually stripping away electrons, ionizing the atoms around the fire until the electrons get recaptured. Microwaves work by establishing a standing wave of electromagnetic fields, which push and pull the electrons stripped away from the fire. This causes them to collide with the air molecules inside the glass, adding heat to the air and stripping away more electrons. This continues until the air is ionized to the point of becoming plasma, dissipating, and then ionizing into plasma again. The reason we can actually see the plasma also comes down to those electrons, as their collisions with the air molecules can add energy to the air’s electrons, which then fall back into their normal energy levels and release light, similar to the effect of fluorescence we’ve mentioned in previous pieces.

If you want to make plasma yourself, get an adult and try it, but please remember to be careful.

How Spinning Magnets Make the World Turn

We all know know what magnets are. At the very least, you’ve probably put one on the fridge. Magnets can come in all shapes and sizes, but they all work the same way. In simple terms, they have a north pole and a south pole. When two identical poles get close, they repel, and–of course–opposites attract.


Some of the many shapes, sizes, and types of magnets. Photos from coolmagnetman.

That said, many things about magnets are a lot more mysterious. Scientists explain these phenomena through something called a magnetic field, and this has some pretty wild and testable consequences. One of them is known as Faraday’s Law, which says that a changing magnetic field can generate electricity through a process known as electromagnetic induction. There isn’t a lot to be said about how this works; just as gravity pulls you down, moving magnets near wire will make electricity!


If this doesn’t seem all that interesting or important then just think for a moment about how much electricity we use. Then consider where that electricity comes from. Coal, wind, and nuclear power probably come to mind–but then how do we get the electricity out of those things? The answer is actually simple: magnets! Each of the major methods of making electricity really are just finding ways to spin a turbine which is connected to a magnet!

The amount of power that you get out of one of these generators depends on how many times the wire is wrapped around, how close it is to the magnet, and how strong the magnet is. This in turn makes the magnet harder to turn. If you look at a windmill, you will notice it has huge blades, allowing it to convert more wind into more power!


This wind farm in Palm Springs not too far from our campus employs this exact technology to generate electricity from the wind! Photo from best of the best tours!

What is an Electromagnet?

Here at AstroCamp, one of our most popular classes is Electricity and Magnetism. At first glance, it might not be obvious how these things are related, but they are actually tied together through important physical principles.

To give you some evidence, let me introduce the electromagnet.


This is really just a metal rod wrapped with a bunch of wire. Without any electricity going through the wire, it doesn’t do anything special. Now, let’s press the button and let electricity flow through the coil!


What is going on? Well, to explain that we have to back up a bit. Let’s start by answering this question: What is electricity? It is the thing that runs our light bulbs, smart phones, computers, and air conditioning but what is it on a more fundamental level? What is happening?

asset-v1-pkuhighschoolph1019999_t1typeassetblockatom-light-640x360As you probably know, everything you have ever touched is made out of atoms, and these atoms have three parts: the positively charged proton, the negatively charged electron, and the neutral neutron. These charges determine how the particles interact; particles with identical charges push away while those with opposites attract.

Electricity, as you may have figured out by looking at the word, has to do with electrons. Electricity basically means moving electrons. However, physics has a bit of a surprise for us here. Whenever a charge is moving, it makes a magnetic field–if this word seems confusing, this is just what is produced by a magnet to push and pull on other magnets–around it in a circle. This happens every single time. You might be tempted to ask why, but I don’t have a great answer for you. This is just how nature is.

All we have done to make an electromagnet is sort of durn this trick on its head. By wrapping the wire into a coil, the circular magnetic field created every time an electron moves adds up in the middle. This kind of design is called a solenoid.


This awesome illustration shows how the circular magnetic fields around each wire add up in a solenoid to make a strong magnetic field inside. All credit goes to Paul Nylander.

This might seem like a simple lab trick to convince you about the mysterious but very real connection between electricity and magnetism, but it turns out to be an incredibly useful and important design. Outside the obvious purpose of picking things up like the giant electromagnets at junkyards, electromagnets are used in speakers, hard drives, MRI machines, motors, generators, and many other things you might not expect!


This is a view inside the Large Hadron Collider at CERN, the most powerful particle accelerator on the planet! This shoots tiny particles at very near the speed of light along a very precise track. While you might expect it to be the metal walls that keep the particles inside, the tiny particles would actually fly right out through the walls! So how do they keep those pesky particles in line? They steer them using incredible powerful superconducting ELECTROMAGNETS! Photo credit CERN.

Written By: Scott Alton

Lightning Electricity in the Palm of Your Hand

During a thunderstorm, lightning often appears to flash instantaneously from cloud to ground, but there’s much more going on than meets the eye! Friction between air currents causes a buildup of negative charge in the lower parts of the clouds. Like charges repel each other, so the excess negatives begin developing an escape route. Strong, invisible electric “feelers”, called stepped leaders, branch downwards through the air.


Lightning over Norman, Oklahoma, 1978. Image credit: C. Clark, NOAA

As stepped leaders inch closer to Earth’s surface, they leave a conducting path in their wake. Their electromagnetic field also NOAAlightning2begins affecting electrical phenomena on the ground. Positive streamers of charge reach up towards the negative stepped leaders. When streamers and stepped leaders meet, an ionized bridge is completed from clouds to ground.

Given an unbroken conducting path to follow, the negative charges built up along the stepped leader flow rapidly into the ground. The lowest charges are the first to dissipate, clearing the way for charges higher up to follow downwards along the same channel. This upward propagation of charge movement emits visible light, as shown in the NOAA gif at left. Stepped leaders emit light, too, but very faintly. Since the whole process happens incredibly quickly, our view is dominated by the brighter return stroke.


Ever been told not to go swimming in a thunderstorm? That’s because water is a great conductor! If lightning struck the water you were swimming in, a massive shock would be efficiently transferred to your body. In this video, the Oudin coil generates a buildup of negative charge (concentrated on the metal tip of the device). When we bring the excess charge near water, artificial lightning arcs both to and through the puddles!

Written By: Caela Barry

Fantastic Plasma

The universe is full of action at a distance. Planets and stars tug on each other via the gravitational force. Magnets attract or repel based on their polar orientation. An object’s area of influence is called its field. Gravity, electricity, and magnetism are some of the most common field interactions.


The plasma ball’s central electrode transmits an electromagnetic field that extends far beyond its glass shell. Need proof? Try holding a fluorescent light tube nearby. The field generates electricity by setting electrons in motion, lighting the bulb!

Inside the globe is a miniature atmosphere of noble gases. These are less dense than air and ionize at relatively low voltages. At the core of this noble cloud, a high-frequency oscillating current creates a large buildup of negative charge. Like charges repel each other, so the buildup discharges outward in lightning-like plasma filaments.


Plasma is the most abundant state of matter in the cosmos. Solids, liquids, and gases are more familiar on Earth, but in the big picture, plasma is everywhere! It’s what stars are made of, and stars comprise most of the known mass in the universe. So, what is this stuff?

MagneticSunAdding energy to a solid weakens the attachments between its molecules, so it melts into a liquid. Add even more energy, and the molecules detach completely– that’s a gas. Plasma is what happens when a gas becomes so highly energized that electrons actually separate from their respective atoms, creating an electromagnetic fluid.

Bring gravity and rotational dynamics into the mix, and some crazy field patterns emerge. The NASA image at right shows the sun’s magnetic field lines. This behavior is the source of stellar weather like sunspots and solar flares, which have measurable effects on GPS and other systems. Large coronal mass ejection events can even blow out power grid transformers on Earth! Aerospace engineers, pilots, and electrical companies get forecasts from the NOAA Space Weather Prediction Center just like most of us check the weather at home.

Written By: Caela Barry

The Circle of Electromagnetism

Electricity is one element of physics that we encounter on a daily basis. It powers our televisions and our computers, and keeps the lights on at home. Magnets are something we think of as less common, only using them when we need to navigate using a compass or stick something to our fridge. But electricity and magnetism are really just two sides of the same idea!

We can see some examples of this relationship using the induction coil. There are two parts, so let’s tackle them one at a time. First, whenever electricity runs through a wire, it creates a magnetic field. If the wire is in a circle, the magnetic field will be the strongest through the middle. By stacking up several loops of wire to make a coil, we can create an electromagnet.


Electromagnetism at AstroCamp. Pressing the button sends electricity through the wire solenoid which is coiled around a nail to create a magnetic field.

Not only can electricity be used to create a magnet, but magnetism can be used to create electricity. When a conductor, like a metal wire, experiences a changing magnetic field, an electric current is created. We can even use this electricity to power a lightbulb! This process is called induction, and it is the basic principle by which electricity is generated in almost all power plants.


Strong neodymium magnets are rotated inside a coil of copper wire, producing a current. The needle moves back and forth, indicating the the current produced in this way is alternating, or AC current.


This wind farm in Palm Springs employs this exact technology to generate electricity from the wind! Photo from best of the best tours!

If you want to learn more about these concepts or just see them in action, there is more about them here and hereCombining both of these ideas, we can see why the small metal ring hovers. Turning on electricity through the coil of wire creates a magnetic field that is felt by the metal ring. Then, through the process of induction, electricity is created in the ring, as you can see with the light bulb example below.



The ring is now an electromagnet with electricity running through it! The magnetic field from the ring and from the coil are pointed in opposite directions, so they repel, causing the ring to hover in midair. By submerging the ring in liquid nitrogen, we can lower its resistance and increase the electric current. A stronger current creates a stronger electromagnet and the ring shoots up to the ceiling!


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