Tag Archives: How it Works

Electricity, Magnets, Motors & Batman

Building something and making it move can be intimidating, but it doesn’t have to be! While building an engine to power a car is a rather complicated task, some motors can be made with just a couple of simple supplies that you can pick up at the hardware store!

What you see in the video is called a Homopolar Motor. The name means that polarity of the motor never switches, which isn’t surprising considering that you’ve probably never see a battery’s ends suddenly switch places. The science that powers this motor is really cool and teaches a neat lesson about electricity and magnetism! To find out how it works, lets take a look at the setup in the video one more time:

Simple Cropped

First lets identify the parts. At the bottom is a very strong magnet, known as a neodymium magnet. This magnet produces a magnetic field–the thing that allows magnets to interact without touching one another. On top of that, there is a battery. Simple. Finally, there is the wire. The wire sits on the top of the positive terminal of the battery, and comes down and just barely touches the magnet on the bottom.

Labeled Parts

The wire is touching both the positive terminal and the neodymium magnet. The magnet is a conductor and is attached to the negative terminal of the battery. This means the two terminals are connected by a conductor and electricity starts to flow! Electricity is just the movement of charged particles. However, the electricity is flowing through an area with a magnetic field from the battery! There is a force known as the Lorentz Force that occurs whenever this situation arises. Mathematically, it looks like this:

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This looks like simple multiplication, but the letters have funny hats. This means they are vectors, which means that they include a direction. This makes multiplying them more complex as the product depends not only on the numbers, but how the directions relate to one another. While this can be confusing, the diagram below includes the current (or moving charges), the magnetic field, and the resulting force. See how it pushes the wire in a circle?


As you have seen in the video above, the picture can get more complicated than this. The wire can be in any shape you can dream up. As long as at least one end of the wire touches the magnet at the bottom, electricity will flow and the motor will move! As far as these motors are concerned, the science is pretty cool, but creativity is the real hero!

Batman cropped

The Leidenfrost Effect

Have you ever played air hockey? There is something strangely satisfying about how the puck slides effortlessly across the table, before finally coming to rest. This same thing happens naturally as well, and its actually some pretty cool science. Lets check out how it works!

When things of different temperatures interact, the warmer object loses its heat to the cooler object. This simultaneously warms up the colder thing, and cools down the warmer thing. This shouldn’t be surprising. Its the reason that snow melts in your hands and make your hands feel cold. However, when things are of vastly different temperatures, it can get a little strange.

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In the video, we are dripping water onto a stovetop that is around 500℉. The water is only about 50℉, but the important part is that the boiling point of water is around 200℉ (technically 212℉ but Astrocamp is at an elevation of about 5600’, which actually lowers the boiling point to almost exactly 200℉) which is much lower than the temperature of the stove.

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When the drops of water hit the stove, the part that hits first is immediately vaporized because of the difference in temperature. This means that the little droplet of water now has a little barrier of water vapor between itself and the stovetop, which it can float around on. The water droplets seem to bounce and skitter around without boiling away. This is what we call the Leidenfrost Effect. For water, this seems to occur at temperatures of at least 400℉.

It is the same thing that allows a person to pour liquid nitrogen over their hand unharmed (Don’t try this at home), or dip their hand in water and then dip it in boiling hot lead (DEFINITELY don’t try this at home)! Cooks sometimes use this to estimate the temperature of their pans and see if they are ready to cook.

Future of CDs and DVDs

CDs are dying.  It’s an unfortunate but inescapable fact as the world transitions to digital downloading.  But while the end may be in site for CDs and DVDs, it hasn’t come yet.  Before that day actually comes, perhaps we should take a quick look at this awesome technology and how it works.

A CD’s base a a polycabonate plastic material that is transparent.  It provides the structure and protection for the layers above it.  Above the polycabonate is a thin layer of aluminum reflective coating followed by another thin layer of crylic and then the label.  The most important part of a CD is that the polycabonate sheet is imprinted with a series of miniscule bumps.  The details of the bumps is a code that is what stores the data on the disc.  The bumps move outward from the center of the CD in a spiral pattern all the way to the edge.  The CD reader move along this track using a precise laser to detect the changes in the bumps and decode the data stored on the CD.

As CDs become less and less useful, perhaps we need to find other uses for them.  One entertaining DIY science trick we can do is to melt part of the polycarbonate sheet and blow it out to create a giant bubble.  Make sure to scrape off the aluminum sheet or else it won’t expand to its full amount.  Enjoy!


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