Increasing the efficiency of a simple electric motor?

  1. Okay, so I have a simple D cell battery, enamel coated copper wire loop and a magnet. I can easily get the copper wire loop to spin if I scratch away part of the enamel (that side which touches the stand) off the ends of the wire, run current through a stand, and position the magnet at just the right position.

    Here's the problem......

    When I run a simple electric motor in this fashion, I'm relying on the momentum of the wire to spin back around, hit the magnets magnetic field, then be spun again (which is not efficient)

    What I need to be able to set up is a simple electric motor like this that allows current to run BOTH ways through the copper wire loop, basically spinning it constantly without having to rely on momentum to spin it back around. I'm having a super hard time figuring out a plan for this pand just wanted to see if anyone could help me out.
  2. jcsd
  3. Why don't you build a homopolar motor like this?
    Last edited by a moderator: Sep 25, 2014
  4. I actually would have definitely preferred to build a motor like that, and I actually wanted too, except I'm required for my class to keep the typical simple motor design (much like this one

    The homopolar design does have one characteristic that I do need, and that's the constant movement of the copper wire without relying on momentum. I just need to be able to take momentum out of the design and then id be set.

    I truly appreciate your input!
    Last edited by a moderator: Sep 25, 2014
  5. K^2

    K^2 2,470
    Science Advisor

    With brushed motor, you kind of have to rely on inertia to carry the anchor through at least part of the rotation. You can improve the efficiency by having multiple coils. Typical cheap DC motors have 3 coils with 2 brushes. It's a pretty efficient design.

    To get it even more efficient, you have to go brushless, but that involves either AC current or complex electronic controllers.
  6. Gotcha! Ill stick to the more simple "cheap DC motors" haha. Thank you for the help!
  7. NascentOxygen

    Staff: Mentor

    Re: Needing to get current flowing in 2 directions

    A photo please, CosB. :wink:
  8. Re: Needing to get current flowing in 2 directions

    Do you mean the loop connects to the battery and the whole thing suspended in air free to rotate. Then you put a magnet close by and try to make it rotate?

    This will not work as motor works by repulsion of the two magnets ( one permanent magnet and one from the loop). Problem is once the loop turn and the pole change and become attracted to each other, then it stop and stuck!!! To make turn continuously, you have to change the direction of the current to keep the two magnets repel each other. That is why motor has the thingy that I think called stratem or something that can switch current direction when turning.
  9. Re: Needing to get current flowing in 2 directions

    NascentOxygen and Yungman, that you for replying! I have an update to my question, so I dont think a picture will be needed for this.

    My professor has told me that basically I can only control one variable of the Magnetic Force equation= qvBsin. I can't really control the B or sin of theta, but what I can do is control the velocity. My idea was just to make the loop smaller. Therefore, a smaller loop= smaller radius. A smaller radius equals a greater centripetal force which is equal to the Magnetic Force. Does that make any since or am I just loosing my mind?
  10. Re: Needing to get current flowing in 2 directions

    As for what exactly im working with, here is a general picture of the setup. My idea was just to make a tiny tiny loop to increase the efficiency, since of a larger one.

    Attached Files:

  11. sophiecentaur

    sophiecentaur 14,696
    Science Advisor
    Gold Member

    Re: Needing to get current flowing in 2 directions

    I think your professor was hinting at the fact that you need a circuit that will make the current flow in two directions - but one direction at a time. This will be necessary if you want the coil to keep rotating.
    I suggest you search for images of simple electric motors and make sure that you search, using the word "commutator" (the name of the device you need to use and understand about).
    Pictures you find will show you the best place to locate your permanent magnet and how to arrange for the coil to keep rotating.
  12. Re: Needing to get current flowing in 2 directions

    So sophicentaur, what if all have is just the wire, magnet, and battery. Is there a way to get a somewhat efficient electric motor out of this besides the basic "scratch the enamel off one side of the axles, connect the current, and position the magnet". Is there somethign i can do to the actual design of the wire loop ( like make it smaller, add tiny loops around a larger loop)?
  13. sophiecentaur

    sophiecentaur 14,696
    Science Advisor
    Gold Member

    Until you have found out about a commutator, there's no point in looking further into motor design.
    I assume you can Google?
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