DIY: Geek out your desk with this homemade homopolar bat signal

If you have a high regard for the Caped Crusader, then carve out a few minutes in your day, gather some copper wire, an AA battery, and a neodymium battery. 

The result of your efforts will be a pretty cool bat signal that you can proudly display on your desk.

The bat signal above is, of course, a fancied-up homopolar motor. For the layman, the name means the polarity of the motor never switches, which is not too surprising because a battery’s end never changes place. 

The way this homemade motor works is pretty neat and an excellent lesson to teach anyone interested in engineering. The neodymium magnet serves as a conductor in this set-up — it is attached to the negative terminal of the AA battery. The wire gets wrapped around the magnet, and bent down to touch the positive terminal of the battery. 

Doing this connects the two terminals of the battery to a conductor which, in turn, allows electricity to flow through the wire. Now, while electricity is, generally speaking, the flow of charged particles, in this particular set-up, these particles are travelling through an area with a magnetic field around it. 

This interaction creates a force known as the Lorentz Force; mathematically, it looks like this:
While the formula above might look like regular multiplication, you’ll note that the “F”, “V”, and “B”, which signify “force”, “velocity”, and “magnetic field”, respectively, have identifiers above them — these identifiers signal them as vectors, which means they have direction. 

What does that mean for the formula? 

Well, it makes it a lot more complicated than it looks at first blush. That’s because the product is not dependent solely on the numbers, but how the directions relate to one another. 

How this works out in the real world, that is, causing the wire to spin in a circle, can more easily be understood via the chart below:

If there’s one thing to remember from this project, it’s the right-hand rule. This refers to the rule that if you orient your right hand with the thumb in the direction of the current, and your fingers pointing out along with the magnetic field, you can assume with certainty that the Lorentz force will come out of your palm. 

But if you’re just looking to create a cool knickknack for your desk, copper wire is pretty easy to bend and shape. Per the GIF below, you can do any shape, thought he Batman logo is clearly the best way to go:

Via: AstroCampSchool.org