We used the same AA battery, the same piece of wire, and a single DC6 magnet. This produced some obvious results, with the battery spinning out of control. This is a good way to demonstrate the motor in front of a large group, where you need motion that's more obvious from a distance. It can be challenging to come up with a stable configuration of the wire that allows it to spin well without falling off. Be prepared to fiddle with the wire a bit to get it right.
Use a piece of solid not stranded wire. We used 18 gauge wire, though other sizes would work as well. We removed all the insulation from the wire before experimenting with it. Technically, you only have to remove the insulation where it contacts the battery and the magnet, but removing it all seemed easier. You can even use smaller discs like the DA2 for this demonstration. When describing how a homopolar motor works, most explanations describe it in terms of a force acting on the wire.
This demonstration clearly shows the wire moving, so it makes matters more obvious and jives well with the technical explanation. Homopolar motors are useful for demonstrating electromagnetic forces and explaining the concepts behind how motors work. Why not? Because it only has one winding — one loop of wire. To get the motion, there are really high currents flowing through the wire.
It's a hugely inefficient use of the battery, demanding much more current than these batteries are really designed for. Caution: With this much current flowing, things get hot quickly.
The wire and the battery can become dangerously hot, so handle with care. We receive a lot of questions about motors and generators, but keep in mind that their design can be very much the same. In the motor, an electrical current makes something move.
Put electricity in and the motor turns that into motion. A generator is the opposite: Motion from some outside power source gets turned into current through a wire. Turn the crank by hand, and the motor supplies electricity. Many electric motors can be used to demonstrate this idea. If you take a motor and turn the shaft by hand, you can make electricity. You just don't get enough voltage out of it.
In our Shake Flashlight article, we used a big magnet moving through a coil of wire with over a thousand turns of wire in the coil, which produces a higher voltage. We are now required to collect sales tax in several states. If your business is tax exempt, learn more here. Login Details. New Account.
It was the first type ever built and demonstrated by Michael Faraday in Although not the configuration Faraday used, homopolar motors can be made out of a single AA or C battery, a single neodymium disc magnet and a piece of copper wire. They have two magnetic poles provided by the single permanent magnet that is used to produce the magnetic field, also required to generate rotational movement. It is called a homopolar motor because, unlike conventional DC motors, the polarity of the magnetic field emitted by the conductor and the permanent magnets does not change.
A homopolar motor creates rotational movement because of what is known as the Lorentz force. This current then flows from the centre of the magnet to the edge where the wire connects, it travels up the wire back to the positive terminal of the battery and the circuit is complete.
But how does this generate movement you may well ask? Well, the key is the direction of the current and the magnetic field produced by the permanent magnet. The direction of the magnetic field is demonstrated by the red arrows and the direction of current is shown by the blue arrows. As the current travels perpendicular to the magnetic field, a Lorentz Force is exerted on the on the conductor the wire which again is perpendicular to both the direction of the magnetic field and the current, generating the spinning motion.
Unfortunately, you will never generate enough power from a homopolar motor to power any domestic appliances but they are great fun to make and really useful for demonstrating the effects of electromagnetism and how electric motors work. Because high currents flow through the wire the battery runs out very quickly.
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