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### Course: Physics library>Unit 18

Lesson 7: Electric motor

In this video we show you how to build a simple motor. Created by Karl Wendt.

## Want to join the conversation?

• If this is a DC motor, doesn't it need a commutator? Is there something about this setup that just acts like a commutator?
• He didn't emphasize it, and I don't think he's doing a great job of explaining the detail, but you only scrape one side of the lead wires. That is to say, you do both of the leads that go through the washers, but you only scrap one side- if you were to magnify the cable, and look at it on end so it looks like a circle, then only the top side would have the insulation scraped off.

What this does is to switch on the electricity when the scraped sides are facing down, and create an electromagnet that then aligns with the two permanent magnets, but the inertia from the rotating mass in the coil keeps it turning so it overshoots and rotates to the position where the the insulation is intact, and the electricity is turned off. The inertia carries it further until the scraped side of the leads turn the electricity back on.
• At why 7 times?
• Just an arbitrary amount of times, he could have done it more or less. The amount of windings would effect the current produced.
• if you were to wind the coil more than 7 times would it go faster?
• YES, because the more you coil the more potential energy the spring gains.
• What are some practical applications of the motor we build?
• This motor could power a toy car. If you mount your battery to your wood block with 4 wheels and a more rigid and large fan wheel, you have a toy car. This motor could power a fan, mixer, music box, mini water pump for plants...
• Can you use a permanent magnet instead of a winding to make it non power consuming?
• Hello Ryanpinrui,

Sorry, what you described is a knows as a perpetual motion machine. I still remember when my design was smashed upon the laws of thermodynamics...

Here is an excellent video that helps explain why: https://www.youtube.com/watch?v=4b8ZsFszE8I

Regards,

APD
• so does it have to be copper wire? and how strong were the magnets you used?
• Where do you get copper coil?
• radio shack has the right wire. just tell them your building a small motor.
• can we use iron wire instead of copper wire?
• Hello Fiza,

Probably not because the wire most likely lacks insulation.

Iron is an acceptable conduction but I do not think it would work for this application. The wire used by Karl in this video (magnet wire) has an enamel coating that serves as an insulator. This prevents the wires in the loop from shorting to each other. Also, for this motor there is a trick at Karl states that you must strip the insulation from 1/2 of the wire. This is a critical step that many people miss. You need the rotating part of the motor to make contact only half of the time. If it receives electricity all the time it will stop in one position...

Good luck and I hope you get the motor spinning soon. It's always rewarding to say - look what I made!

Regards,

APD
• Can you add a switch to it?And how?
• Technically, the alligator clips are a form of switch. Removing one will break the circuit and switch the motor OFF. When both are attached, it is ON. A switch just changes the layout of the circuit, either breaking it or completing it at a certain point.

In this case, everything was in series (i.e. on the same track). If you had things in parallel (two or more tracks), you could make it so that some things are on while others are off, depending on where you chose to disconnect the circuit.
(1 vote)
• Is it ok to use duck tape?If you don't have the tape he used for the video.