What you need:
- AA battery
- Neodym magnet (cylinder 15 mm diameter, 8 mm height, search google for "super magnet" store)
- 30 cm copper wire 1.5 mm² (from a 3 x 1.5 installation cable)
- 5 mm screw / bolt
- Hammer, scissors, flat nose pliers, wire cutter, wire stripper
What you will get at the end:
A motor built with just three parts (Battery, magnet, wire) in less than ten seconds:
How to build:
We need to prepare the battery first. Take the bolt and the hammer and make a dint into the flat battery pole (marked with “-“). This dint will help to keep the wire in place when it starts rotating.
Now place the other end of the battery onto the magnet. As the battery has an iron sheet case, it will cling to the magnet. We don’t care which end of the magnet sticks to the battery “+” pole.
The magnet is quite heavy, so it is a perfect base when you place the battery upright onto your table.
Now comes the tough part: We need to bend the wire. You could take a 3 x 1.5 mm² installation wire and strip off the outer insulation. Then take on of the three wires and strip off their insolation. We will need about 30 cm of uncoated 1.5 mm² copper wire. If you do have a wire stripping tool at hand, this will help a lot getting rid of the insulation.
Take this wire and make a sharp bent right in the middle. Use flat-nose pliers to get this bent as pointed as possible.
Next, bent both sides with a 180° turn so that the ends do point into the same direction as the sharp middle bent.
The gap between the two wire ends must be big enough to give room for the battery without touching it. At about 3 cm below the middle point, bend both ends outward.
2.5 cm later turn them back inwards so that they both get in touch in the middle of this shape.
We now need to bend both ends circularly with a diameter round about the size of the AA battery. The circle needs to have the same orientation as the diameter of the battery. When you place the middle point on the battery’s dint, this circle must not touch the table. It needs to contact the magnet’s outer diameter.
If you’ve bent this shape right, the wire will spontaneously start rotating around the battery.
If it doesn’t, here are some hints:
The shape should be as symmetric as possible. It should perfectly balance on the middle point. The wire circle which needs to get in contact with the magnet should not rub too tightly. It needs just a very loose touch. Use a fresh battery because this requires a lot of energy. If the wire circle only gets intermittently contact to the magnet, the battery will last longer, and the wire might turn faster.
Please note that the wire and battery might get hot when you operate the motor longer than 30 seconds.
How it works:
Magnets are friends of electricity: When you run electricity through a wire, it is producing a magnetic field around it. And when you move a magnet over a wire, the moving magnetic field produces electricity inside the wire. This is called “electromagnetic induction”.
The battery is like a current pump. It pushes electrons inside the wire. You can think of electrons as little electricity pets queueing inside the wire. As soon as the battery pushes an electron into the wire, the other electrons inside the wire step forward, and at the end of the wire the las one will fall out. Electric current is nothing else but electrons moving along a wire.
Our wire is quite thick, and that is why many electrons can pass it per time. So there is a strong current passing the wire. But current is not only flowing through wires. It runs through the magnet too because the magnet has a metal coat. If material like metal let current flow, you call such material a “conductor”. It conducts electricity. The magnet is in contact with the battery’s plus pole. That’s where the electrons get sucked in again. So they circle because the battery is kicking them to do so. This is why you call something like this an electric circuit. This word comes from the word “circle”.
But why is the wire moving? If a strong current flows through the wire, this will result in a strong magnetic field. The wire becomes a magnet. The poles of this magnet are oriented so that this magnet is pushed away (repelled) from the strong Neodym magnet. That’s why the wire starts moving. It wants to get away from the Neodym magnet. But it can’t leave. It is escaping in circles. That’s a little bit like riding on a carousel. The centrifugal force wants to get you away from the centre of the carousel. But your seat is chained to the carousel and can only circle. If the chains tore off, you would fly straight away from the carousel.
You can turn the magnet over so that its opposite pole touches the battery. The magnetic field is now inverted. And therefore the wire turns also the other way around. Your motor runs in backward gear.
By the way:
Such a simple motor is not strong enough to pull anything. Strong motors are constructed different and a little bit more complicated.
If you’re back to school, take the three parts with you and show them to your teacher. Then ask her if she believes you can build a motor out of these three parts in less than 10 seconds. If she will not believe you, just take the pieces and assemble your motor in front of her eyes. And because you’re smart, you go on explaining to her how this motor works. And to completely baffle her, tell her this motor is called a “homopolar motor”. Your family might get the first price in homeschooling J.
Where did I find the idea:
What's coming up:
Next week, we will let a pencil levitate in the air.