Tag Archives: Electricity

How Does a Speaker Work?

It’s easy to look at a piece of technology (like a speaker) and feel like you’re looking at a black box, wondering how they work. What’s hidden inside them? It must be complicated, right? Often times, that holds some truth. But you would be surprised how far you can get if you can nail down just a key concept or two. To understand how something like a speaker works, the inherent link between electricity and magnetism is one of those concepts. 

This link between electricity and magnetism is most often used by creating one from the other. Magnetic fields can create (or induce) electric fields. For example, our hand crank motor moves a wire around a magnet, and this changing magnetic field induces an electric field, which we can use as electricity, to do something like light up a lightbulb. The phenomenon of inducing an electric field from a magnetic field has given a straightforward name of electromagnetic induction.


 And, lucky for us, induction goes both ways: electric fields can also induce magnetic fields! We have an electromagnet at camp that turns a screw into a magnet. Around the screw is a coil of wire, and pressing the button allows electric current (from the outlet) to flow through the coils that, and that electric current induces a magnetic field– creating a temporary magnet out of the screw.


Inside a speaker, you’ll also find a type of electromagnet… using coils of wire wrapped around a permanent magnet. Pulses of electricity carry sound information from your phone down through the coils of the electromagnet, rapidly changing the direction of the magnet’s magnetic field back and forth, which creates alternating magnetic forces, and these forces are what moves your speaker cone back and forth, AKA creating sound! 

To create your own speaker, you need a 2 to 3 strong magnets, enamel wire (copper wire with a thin insulated coating), and something cone-shaped to funnel the sound. We used a phone to play music, and opted to use an aux cord and alligator clips to connect the copper wire to the headphone jack. Make sure to use the 1st and 3rd section of the aux cord. (You can also sacrifice a headphone jack and wrap the exposed wires around the two ends of the copper wire.)  When using the enameled wire, you need to sand the ends of the wires down so that the copper wire is showing. (You won’t get a connection if you don’t). Wrap the wire around the magnet (the more turns, the better the results!) and use another magnet on the other side of your sound funnel/speaker (we used a bowl). This magnet helps the speaker work better, and has the added result of keeping your magnets easily attached to the speaker. When you put these all together, you should have a speaker! 

Tip: The speaker works off induction, and the more you have of it, the better results you’ll get. To increase induction, you can increase how many turns and how big the coil of wire is, and you can increase the strength of magnets. 

speaker full setup close

Electricity and magnetism are complicated subjects to study, but you don’t need years of studying to take advantage of it. By knowing the idea of electromagnetic induction, you now know how a simple motor is made, and can make one too [https://astrocampschool.org/homopolar-motorcar/] ! From speakers, to washing machines, to windmills, the power of wires + magnets basically endless, and integral to our way of life! In a world surrounded by motors and electromagnets, you’ll never look at your world the same way.

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


Electric Motor DIY

An electric motor is a device used to convert electrical energy to mechanical energy. Electric motors are extremely important in modern-day life. They are used in vacuum cleaners, dishwashers, computer printers, machine tools, cars, subway systems, sewage treatment plants, etc, and you can make your own at home! Here’s how:


  • Copper wire
  • D battery
  • Magnet
  • Electrical tape
  • Scissors

electric diy


Coil the wire around a battery about 30 times. Wrap the extended ends of the wire through the coil, securing the coils in place.

Step 2:

Carefully file the enamel off of the bottom half of the extended portion of the wire.

Step 3:

Secure one wire post to each end of the battery, creating a small U-shape to cradle the coil.

Step 4:

Slide a magnet onto the battery.

Step 5:

Place the coil onto the posts and give it an initial spin!

diy electric 2

Electricity will flow from the battery through the coil of wire. Moving electricity induces a magnetic field in the coil, which opposes the magnet half of the time, and is attracted the other half. Give it a flick and watch the electrical energy from the battery be converted into the mechanical spinning you see!

Written By: Mimi Garai

Wind Power at AstroCamp

Wind farms are a common sight these days, but humans have been using wind power for about 2,000 years. It wasn’t always for electricity, however, but to mill grain into flour, operate an organ, or pump water. How does a windmill do any of that though?

When you see a windmill, the part that sticks out most is also the most important: the blades. Blade designs and orientations have changed through the centuries, but they all serve the same purpose and have the same drawbacks. If a windmill has too few blades, the weight of the windmill is imbalanced and will have too much open area, catching very little wind and making it increasingly difficult to actually rotate to blades. Too many blades, and the windmill will be too heavy to easily move in the wind. In either case, power generated by the windmill suffers. Most wind turbines have three blades, and that’s the amount we see most commonly in our whirling windmills class here at AstroCamp.

Wind Power 1


Number of blades is not everything though, as you can see above; the angle of the blades plays an important role as well. Our windmill has the usual three fins, but isn’t even moving because its blades are flat against the wind. When the wind hits the blades, it just pushes them back. Once you angle the blades, the wind begins to push the blades back as well as up or down, allowing the windmill to spin. The fins must be angled consistently, however, as if blades on opposite sides are both being pushed up, they will cancel one another out and the windmill will still not move.

Wind power

Adjusting the angle of the blades brought our windmill up to generating over 17 milliamps of current, though campers have gotten over 60 mA with theirs. That’s just the current generated from a tiny windmill in front of a fan, real wind turbines generate enough electricity to power thousands of homes and there are nearly 50 thousand wind turbines in the United States alone.

Wind Power Final

Static Electricity: It’s Shocking

Have you experienced rubbing your feet on carpet just to reach out to someone and give them a little zap? Or slide down a plastic slide and gotten a nice jolt from it?  What about rubbing a balloon on your head to make your hair stand on end? A Van De Graaf generator is a tool to experience even more static electricity!

Static Electricity Hair

Static electricity is an imbalance of electric charge on a surface. The charge remains imbalanced until there is an electric current or an electrical discharge. A Van De Graaf generator works much the same as rubbing your feet on the carpet to move electrons throughout your body. A moving belt in the generator accumulates an excess of electric charge which is then transferred to a large hollow sphere.

Static Electricity Fur


The sphere builds up  free electrons which all have a negative charge. When too many negative charges are near one another they will start to repel. If you force enough of them onto a single surface you can build up enough charge to see an effect such as your hair standing on end, pie tins flying off due to repulsion, or a shock!

Static Electricity Hat

Electricity will  take the path of least resistance and wants to be neutral. As shown here, a fun and safe way to manipulate the static electricity is with a grounding rod. The grounding rod neutralizes the Van De Graaf generator by moving all of the excess charge from it to the surface of the Earth.

Static Electricity shock

You can also neutralize the generator without a grounding rod. Humans are decent conductors of electricity. This means that your body could act as a grounding rod too. Just remember that you have one thing that a grounding rod does not…NERVES. If you decide to ground the sphere, brace yourself for quite the jolt!

Written by: Mimi Garai

DIY Soda Battery

Elementary school students the world over are familiar with potato batteries or lemon batteries, but did you know you can make a battery from soda? With just some wire, two different kinds of metals, and your favorite soda, you can build your own battery!

All you need to do is connect your metal plates to one another with a wire (or connect them to a multimeter as well to measure the battery’s voltage like we did) and place your plates into the soda. Make sure your plates aren’t touching during this experiment because if they touch, the electrons won’t flow through the wire and you won’t see a voltage register on the multimeter.

With our battery, the two metals we’re using are zinc and copper, as zinc is more reactive with the soda than the copper is; leading to a more significant voltage produced by the battery. You could also use the aluminum of the soda can, but you would need to remove the coating from the can with steel wool, as it is designed to prevent the aluminum and soda from reacting with one another. You need two different metals because if both plates are reacting with the soda the same amount, there’s no need for electrons to flow between them and therefor very little voltage produced like you see below when we try making a battery with two copper bars.

To understand how the voltage is generated, let’s take a look at the soda itself for a second. Within the soda is phosphoric acid; the key ingredient to this whole process. That phosphoric acid is breaking up into positive hydrogen ions and negative phosphate ions. Those phosphate ions are attracting the positive nuclei of the zinc and copper atoms, but copper holds its atoms together a little better than the zinc. As a result, a lot of electrons from the now separated zinc atoms are left over in the bar, some of which flow through the wire into the copper bar and establish an equilibrium.

The zinc bar is now fairly close to neutral, but the copper is more negative, so it attracts the positive hydrogen ions which remove some of the excess electrons and combine to form hydrogen gas. That gas floats up through the soda and out of the system. This process is happening in a continuous, rapid cycle so electrons are always flowing from the zinc to the copper.

Over time, the copper bar will start to become slightly positive and will repel some of its positive ions into the soda, some of which will encounter the excess electrons on the zinc bar and form a black coating of copper and copper oxide around the zinc. When that has gone on long enough, the zinc in the soda will be completely coated in copper and the voltage will look like our attempt with two copper plates above, eventually killing the battery.
When we tried with a different soda, Sprite, the voltage produced was roughly the same, but the battery lasted a lot longer because of the stronger acid in the Sprite. Grab your favorite soda and see how much voltage you can generate!

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 Color is Lightning in a Beaker?

Thunderstorms can be incredible to experience. From the bright flash of lightning that is often almost to fast too see, to the immense crack of nearby thunder that can make your heart feel like it skips a beat, they truly are a demonstration of the power of nature.


Image Credit: NASA

They are also full of interesting science! For instance, lightning usually carries between 100 million and 1 billion volts of electricity! This allows it to jump all the way from clouds to the ground, and as it does so, some of that energy is transferred to the atoms in the air. This energy is released as light, which is how we see it. 

This means that it is the air itself which determines what the air looks like. On Earth, our air is made up of about 78% nitrogen, 21% oxygen, and a bunch of other gases like water vapor, carbon dioxide and argon. When we put electricity through it, it gives off a characteristic glow:


The Oudin Coil generates up to 50,000 volts of electricity–much much less than a thunderstorm. This allows the electricity to jump about an inch, rather than the miles between clouds or to the ground of an actual lightning strike. However, when it arcs through the air, this still produces a similar look and identical color1.

Lets see what it would look like in a different environment. The beaker in this gif has a bunch of dry ice–which is just solid carbon dioxide–at the bottom. Unlike regular ice, dry ice doesn’t turn into a liquid, but instead skips straight to carbon dioxide gas! This gas is more dense than air, so the beaker ends up full of just carbon dioxide, which is a much different composition than our atmosphere. Check out what happens to the lightning in there!


Unfortunately, we can’t try this particular method with every gas for several reasons. First of all, not all gases are heavier than air. This would make it hard to keep it in the beaker. In addition, other gases might explode, or worse, if exposed to electricity with oxygen around in this way. Still other gases can be very toxic. Fortunately, we have some tubes of gas and a machine that puts electricity through it in a similar way. In this gif, the gas tubes are viewed through a diffraction grating which breaks up the light into the different colors of the rainbow contained within. This is actually a whole different branch of science which is used to figure out what elements different things are made of just by seeing the light that comes from them! Learn more about that here.

Written By: Scott Alton
1People actually report lightning to be many different colors. In general, nearby lightning will have a purple glow due to the composition of the atmosphere, and the central part will look white simply because it is so overpoweringly bright and doesn’t give time for eyes to adjust. Most other colors that are reported are because the lightning is being viewed from a long ways off and the light has to travel through dust, rain, haze, pollution, or other things that can change its color.

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


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