Homopolar Motor

This very simple electric motor is called a homopolar motor because the magnetic field does not change direction or strength. With only three parts, it is probably the simplest motor you can possibly make.

126 Comments:

1. Jan 31, 2007 | 10:43 pm

   Sum1 wrote:

   Is the magnet radially magnetized?

2. Jan 31, 2007 | 11:28 pm

   Dangerously Fun wrote:

   @Sum1:
   No, axially. (The flat sides are the poles.)

3. Jan 31, 2007 | 11:36 pm

   garyj wrote:

   Where do I get the magnet from?

4. Feb 1, 2007 | 12:00 am

   Dangerously Fun wrote:

   @garyj:
   I buy the magnets online, because normal stores do not have a good selection. There a couple of decent shops online - I prefer K&J Magnetics. Here are the ones I used.

5. Feb 1, 2007 | 12:02 am

   Stark wrote:

   Will it work with any size battery? (i.e. D or C cell)

6. Feb 1, 2007 | 12:06 am

   abcde wrote:

   Stark: Bigger batteries (or perhaps a stronger magnet) should not only work just fine, but better. If it doesn’t spin faster, it should at least last longer.

7. Feb 1, 2007 | 12:11 am

   sam wrote:

   Ok. So is the copper wire barely touching the magnet? I’ve tried several different bends of the wire, but it just isn’t spinning.

8. Feb 1, 2007 | 5:51 pm

   Dangerously Fun wrote:

   @sam:
   Yes, the wire has to touch the magnet consistently but not squeeze it too tightly.

9. Feb 1, 2007 | 9:41 pm

   harchim wrote:

   I got it working, its pretty cool.

10. Feb 2, 2007 | 6:30 am

    GoGreen wrote:

    Showed this to my nerdy genius friend (his latest project was LED throwies, so he had the magnets lying arond), he flipped his top. I think he’s going to invent a car that runs on these motors or something.

11. Feb 3, 2007 | 9:42 am

    Ashish Mohta wrote:

    Great Post.Its really interesting to see the creativity of the brain

12. Feb 4, 2007 | 12:32 am

    AC wrote:

    I can’t get the wire not to immediately stick to the magnet.

13. Feb 4, 2007 | 12:55 am

    Dangerously Fun wrote:

    @AC:
    Copper is not attracted to magnets. If your wire is being attracted to the magnet it isn’t copper.

14. Feb 4, 2007 | 2:25 pm

    Kurrus wrote:

    Woah cool!

15. Feb 4, 2007 | 8:26 pm

    Johan wrote:

    How long will it last with just a regular AA?

16. Feb 5, 2007 | 8:02 pm

    gollyjeepers wrote:

    Johan:
    It won’t last long; you are short circuiting the battery. You are essentially running the wire between the poles of the magnet. The most amps possible are in the circuit.

17. Feb 7, 2007 | 10:38 am

    Pseudonym wrote:

    But how does it work?

18. Feb 7, 2007 | 10:44 am

    tezla wrote:

    Probably best NOT to try this with a NiCad or NiMH cells as they might deliver enough current to heat the wire, burn fingers etc. best stick to small non-rechargable cells.

19. Feb 7, 2007 | 10:47 am

    Anonymous wrote:

    How does it work?.. It’s a permanant magnet motor dude. The magnet provides both the magnetic field and a slip ring/comutator for the “winding”.

    Who will be the first to bend one with more than one “turn”.

20. Feb 8, 2007 | 8:33 am

    JP wrote:

    Does it work with every magnet??

21. Feb 9, 2007 | 7:45 am

    HorneT wrote:

    does it work with an magnet from a speaker, too?

22. Feb 9, 2007 | 9:39 am

    Dangerously Fun wrote:

    @JP, @HorneT:
    Neodymium magnets are necessary because 1) they are much stronger and 2) they have a nickel surface that both conducts electricity and allows the wire to slide easily.
    Update: It has been suggested that you can wrap a standard ceramic magnet with aluminum foil to make it conductive. However, if you do this your motor probably won’t spin as fast as it would with a neodymium.

23. Feb 9, 2007 | 6:49 pm

    Eyeball wrote:

    I dented the top of the Positive battery dimple to gave it a slight recess. This acts like a bearing pocket so the wire stays in the recessed dimple.

24. Feb 9, 2007 | 9:51 pm

    Dangerously Fun wrote:

    @Eyeball:
    That’s a great tip.

25. Feb 10, 2007 | 4:52 pm

    SJShadow wrote:

    this is the koolest thing eva!

26. Feb 14, 2007 | 12:30 pm

    Anonymous wrote:

    If your wire touches table u just need to put it on some coins

27. Feb 16, 2007 | 9:17 am

    Mustafa wrote:

    Nice Experiment. Its really interesting and good to see that people love to share their knowledge.
    I want to ask you that I couldn’t get magnet anywhere, none of the hardware shop had that near my hometown. Plz help me out with this problem.

28. Feb 16, 2007 | 11:05 am

    Dangerously Fun wrote:

    @Mustafa:
    They are difficult to find at local stores. I suggest buying them online. I use these.

29. Feb 17, 2007 | 9:34 am

    Tom wrote:

    I have the mags and can’t wait to try this, but something just occurred to me. The copper wire cannot become magnetized; if the wire cannot become magnetized it cannot act as an armature. How does the wire begin to spin if it is immune to any magnetic field regardless of how strong it may be?

30. Feb 17, 2007 | 12:50 pm

    Geert wrote:

    Tom - If you let a electrical current run in a conductor there will be a magnetic field in it. It doesn’t matter what material the conductor is make off…

31. Feb 17, 2007 | 10:52 pm

    Jeebis86 wrote:

    Is there anyway that ths could generate enough energy to power something? If so please tell.

32. Feb 18, 2007 | 2:32 am

    Foko wrote:

    Jeebis86 - Don’t know why you ask this, but nope, you are actually using lots of electric current and transforming it to a spin. Which has almost no torque… energy wasting system, better using the battery’s energy directly for anything else.

33. Feb 19, 2007 | 11:25 am

    Anonymous wrote:

    It was awsome but don’t let your pets see it

34. Feb 19, 2007 | 8:25 pm

    i wonder wrote:

    does the copper wire have to be a whole or can it be a strands of wire like out of a cord at home

35. Feb 22, 2007 | 7:31 pm

    Dangerously Fun wrote:

    @i wonder:
    I think it will work with stranded wire, but you’ll just have to try it.

36. Mar 1, 2007 | 1:56 pm

    Ant wrote:

    Once the copper stops spinning, is all of the power from the battery gone?

37. Mar 1, 2007 | 3:46 pm

    Dangerously Fun wrote:

    @Ant:
    Yeah, most likely the battery is drained.

38. Mar 1, 2007 | 8:28 pm

    tsmith wrote:

    does the magnet have to be bigger than the battery end?

39. Mar 1, 2007 | 8:50 pm

    chuck wrote:

    tsmith - Not necessarily. It does make it easier if the magnet is slightly bigger so the wire slides over the battery easily.

40. Mar 3, 2007 | 1:52 pm

    chris wrote:

    my grandpa and i are going to make one of these today

41. Mar 4, 2007 | 12:10 am

    Computerchi wrote:

    It is amazing the number of people you can get interested by just spining a copper wire on a copper top. I guess it is the simplicity of the gizmo.

42. Mar 5, 2007 | 4:52 pm

    chris wrote:

    hey i was wondering how you made those perfectly shaped pieces of copper?

43. Mar 5, 2007 | 5:27 pm

    Dangerously Fun wrote:

    @chris:
    Mainly it takes time and patience. Use needle nose pliers to help you make the sharp bends, and to make smooth curves bend the wire around something round.

44. Mar 5, 2007 | 9:47 pm

    Dangerously Fun wrote:

    For those wondering how it works, this engineer published an explanation.

45. Mar 10, 2007 | 12:46 am

    zeldisland wrote:

    I built one with my 1/8″ magnet and it didn’t work… so I used a stack of em and wrapped the wire maybe 8 times. Then I thought I’d put on a resistor (don’t know the size) and it’s been running for an hour more or less… it’s messy and keeps falling off :)

46. Mar 14, 2007 | 3:03 pm

    e3e wrote:

    wow dude… that is so awesome… i’m doin this for a science project for skool! thanx for the idea… this is gonna rock the skool! lol… just kiddin but it is pretty cool.

47. Mar 16, 2007 | 1:26 pm

    yoman wrote:

    its harder to make the frame than i expected

48. Mar 16, 2007 | 8:11 pm

    Steve wrote:

    this is soo cool and i was eager to try it out… i found just a household magnet that fit around the bottom of the battery like the one above and i start out with the copper wire… MAN that is so hard to bend to fit !! it took me almost an hour… the wire i was working with was thick and even after placing it on i had to tap it to get it spin about 5 times then stop… very cool tho

49. Mar 18, 2007 | 2:34 pm

    Scout man wrote:

    would it work if you put something like a small LED light halfway along the copper wire so that you dont short out the battery, possibly even making it last longer?

50. Mar 21, 2007 | 4:22 am

    Mark wrote:

    Scout man,
    The resistance has to be minimal, an LED or light will stop it from working at all. With this kind of Lorentz-force device, you need as large a current as possible. The more amps the better. It’s a bit like a railgun, but in a loop.

51. Mar 21, 2007 | 5:42 am

    Corruptioo wrote:

    yeah, i got his to work with a weak magnet, and a AAA… you really don’t need to over do it that much…

52. Mar 22, 2007 | 7:46 pm

    Calvin wrote:

    Sorry to comment again, if adding another battery, would it possibly be spinning faster?

53. Mar 23, 2007 | 1:40 am

    Ganja wrote:

    I would think not for faster, i’m fairly certain the battery is already using as much power as possible and adding anything else would in theory only create more resistance, it does however work tho

54. Mar 23, 2007 | 12:59 pm

    Ganja wrote:

    If anyones looking for a decent piece of wire may I suggest a piece of coaxial cable works like a charm

55. Mar 25, 2007 | 11:19 am

    cghsiahi wrote:

    it got a small bit to do with the magnet on the bottom basically as you know current flows through the wire and back to the battery and the magnetic field that the magnet gives off acts at right angles to the current so it spins

56. Mar 27, 2007 | 9:28 pm

    OC wrote:

    what gauge wire are you using?

57. Mar 29, 2007 | 12:14 pm

    Morgan wrote:

    The gauge of the wire doesn’t matter. However, if the wire is small and you use a large battery you may heat the wire. The ceramic magnets don’t work because ceramics are insulators and there for no current flows through the wire. Also the more powerful the magnet the larger the torque on the wire is going to be.

58. Mar 30, 2007 | 9:32 am

    gary wrote:

    cool it works with headphone magnets

59. Apr 8, 2007 | 6:57 pm

    siegerson b wrote:

    it is hard to get to work, but its worth it in the end. write a presentation and score some + points in science =)

60. Apr 9, 2007 | 6:02 am

    siegerson b wrote:

    i used a C battery and 14 gauge wire. works just fine, but it is s little slow, i dont care

61. Apr 11, 2007 | 1:59 am

    Anonymous wrote:

    i have trouble getting the copper wire to spin. does the primeter of the magnet have to have copper wire around it or just a little bit constantly touching the magnet

62. Apr 12, 2007 | 9:43 pm

    MonkeyMshr wrote:

    If the wire is touching the table, workbench, etc., etc it wont work because there is too much friction on it. If u can use 3 magnets instead of 1 . Then make the copper touch the top magnet, and it should start spinning. ;)

63. Apr 14, 2007 | 9:29 pm

    The Blunt Ninja wrote:

    Alright, some people obviously are unfamiliar with the Laws of Electromagnetism. 1: A moving current generates a magnetic field (a moving current can be through a conductor like the copper wire, or through empty space like in a TV tube). 2: A magnetic field exerts a force on a current carrying wire. 3: A changing magnetic field near a conductor generates a current (this is how generators and power plants function).

    The magnet is also a conductor, being coated with Nickel. The current flows from one end of the battery to the other via the copper wire (+ to -, or if you’re a chemist, - to +). Now there is a moving charge. The magnetic field from the magnet now exerts a force based on the orientation of the wire in relation to that field, in this case it exerts a force that continually changes, making it spin. The only thing this will do is drain your battery and look frickin’ awesome. It won’t make anything run more efficiently or beat your eggs for you.

64. Apr 15, 2007 | 10:50 pm

    paramag wrote:

    You will see nothing changing. The magnet never changes. It must be the current from the battery.
    Arc welding is based on this because the melting metal pulls current away from the coil but the Counter EMF from the coils’ field colapsing puts current back into the circuit. Could this be the reason the current changes? hmmm? Perhaps/hmm?

65. Apr 16, 2007 | 9:37 pm

    wikisearcher wrote:

    The homopolar dynamo or “Faraday disk” gave very little yield also but did prove some principles like this project does. The short amount of wire requires so much current that it just isn’t practical. There was a huge disk that put out about 5 Mega joules but is a piece of sculpture now.

66. Apr 21, 2007 | 8:01 pm

    charmrus wrote:

    propel the wire, ie. as would water turn a waterwheel, and recharge your battery when drained

67. Apr 23, 2007 | 6:50 am

    Anonymous wrote:

    Easier visual explanation: Use Fleming’s left hand rule (see wikipedia for diagram). Consider the horizontal wires at the bottom of the first design: Magnetic field is vertical (updown direction), current is running along the wire (leftright direction), the resultant force on the wire is either in or out of the page (depending on whether the magnet has N up or down).

    Hmmm… I wonder if it’s possible to make this without a permanent magnet at all… Just coil the wire around the battery forming an electromagnet. Would be much better with an iron core, which is, I assume, how the non-neodymium magnet versions work (forming an electromagnet out of the weak magnet by coiling the wire around it a few times… in fact, I think just an iron core will work: anyone tried it yet?).

68. Apr 25, 2007 | 6:49 pm

    Perpetually Amazed wrote:

    Sweet. I should try this; my science teacher is an idiot and will probably be amazed and actually give me extra credit for once…

69. Apr 30, 2007 | 3:19 pm

    Icy Cold wrote:

    I belive the real question to all of this is, does it even produce power or is it just for show.

70. May 1, 2007 | 12:26 pm

    The Obvious wrote:

    The battery powers the operation. As mentioned before, you could charge the battery by turning the wire in the opposite direction (i.e. inserting energy into the system). I am dismayed that someone would think that it would produce energy on it’s own.

71. May 12, 2007 | 11:46 am

    Mr Beck wrote:

    Thought:
    I know this would be highly impractical, but what if the wires were made to be superconducting? If I understand Ohm’s law, would this not make neary infinite amapage and therefore really huge torque?

    The rock: any size should work but too thin and will get crazy-hot.

72. May 14, 2007 | 7:53 pm

    Seattle Dad and Son wrote:

    I did this with my 8 year old son for his extra-credit homework at school. It took us a while to get the wire shaped properly, but once we did, it spun like crazy! Fun stuff.

73. May 16, 2007 | 9:38 pm

    anon wrote:

    Most copper wire that does not appear insulated actually has a varnish. This must be scraped off at the contact points for this to function. A light tap may be necessary to start the motor in motion. Finally, the voltage of AAA, AA, C, and D cells is 1.5 volts. Thus, the spin rate will not change with a different size battery, though the duration of spin will.

74. May 16, 2007 | 9:40 pm

    anon wrote:

    Addendum:

    Mr. Beck: Though your idea is on principle correct, you are describing a battery short, which will nearly instantly drain the battery. Multiply something nearly infinite by something nearly zero and you get something very finite.

75. May 24, 2007 | 4:35 am

    Person wrote:

    Has anyone tried using resistors to control the spin? Or for that matter, to be able to use a NiCd/NiMH battery without creating a little bomb?

    I know homopolar motors need a lot of current to work, but since Nickel chemistry batteries can put out SO much more current than conventional alkalines, surely a good choice of resistor somewhere in the design would allow you use use a good NiMH/NiCd battery without destroying it?

76. May 24, 2007 | 11:25 pm

    caboose wrote:

    hey does the coil wrap between the battery and the neodymium magnet?

77. May 25, 2007 | 3:31 pm

    Dangerously Fun wrote:

    @caboose:
    No, it just rests on the side of the magnet.

78. Jun 4, 2007 | 1:53 pm

    John wrote:

    A couple of points regarding the electronics in relation to some of the above comments.
    The motor works because it creates a very strong magnetic field in the wire due to the current flowing in the wire, reducing the thickness of the wire will
    do two things, make it get hot and reduce the current flow thus having a negative effect. Putting an LED inline with the wire would result in a blown LED as to much current would flow through the LED, you would need a resistor of the order of 600ohms at least, and you would have to consider the wattage rating of the resistor would need to be quite high, inserting such a resistor would also reduce the current flow to much and prevent the motor working. With regard to using another battery, it would only work if it was connected in parallel so that more current can be delivered, connecting two in series would double the voltage but halve the current so no good. Finally it should come with a warning, shorting batteries, especially high power ones (not just ni-cads etc) is dangerous and could result in the battery exploding. Oh and yes using higher power batteries with a resistor would work in theory but you’d need a high wattage resistor which would be to difficult to place in circuit due to it’s size and weight.

79. Jun 7, 2007 | 8:19 pm

    Gerikault wrote:

    I don’t have neodymium disc magnet. But i cover a simple magnet disc with aluminium foil. It works so fine… :D

80. Jun 20, 2007 | 8:26 am

    Dangerously Fun wrote:

    @ Gerikault:
    Great idea.

81. Jun 22, 2007 | 5:39 pm

    Dogbone45344 wrote:

    you could make a small but short lasting fan with this right?

82. Jul 5, 2007 | 4:04 pm

    zero_7525 wrote:

    This is a nice idea, reminds me of the coilgun, but making the frame for the homopolar motor is very HARD

83. Jul 25, 2007 | 3:35 pm

    Gohlool wrote:

    WOW! Thanks. Worked for me wonderfully!
    Cheers

84. Aug 25, 2007 | 1:11 am

    Justin wrote:

    To make this more fun add wings. Upon doing this correctly the rotating part of my motor would gain a small amount of lift, then breaking the connection, slow and fall quickly, only to begin spinning and lift again. It was an amusing addition.

85. Aug 25, 2007 | 9:57 pm

    radiohedpe wrote:

    very very interesting…my friend chris knows this kind of stuff…thanks for posting it and sharing it with the world…

86. Aug 29, 2007 | 7:43 pm

    putnam wrote:

    finally a use for the 20 yards of wire in my basement!

87. Aug 31, 2007 | 4:54 am

    Anonymous wrote:

    I tried it and it works for about half a minute. I am not sure if the battery got drained during this time or the life of the battery I used were already near the end of their life.

88. Sep 12, 2007 | 3:06 pm

    Simon wrote:

    Neodymium is also the latest magnet technology. Your homopolar motor with neodymnium magnet is much powerful than with an Alnico magnet

89. Sep 14, 2007 | 5:55 pm

    snow wrote:

    Shouldn’t the wire cut the magnetic field at 90 degrees to create torque

90. Sep 18, 2007 | 6:34 am

    irolo! wrote:

    that sounds like suck a cool thing to have in your room. or somthing i can get a good grade in active phisics

91. Sep 25, 2007 | 4:29 am

    mrfixit wrote:

    Great stuff! Thanks to all who run this site.
    The utter simplicity of the homopolar motors catches people off-guard, like a good magic trick. It seems impossible, yet there it is, right in front of your eyes.
    To the ones who are having trouble getting their motors to work, I say keep at it and keep on tweaking ’cause it’s really worth it. Like snowflakes, no two designs will be the same; each creation will require its own final tweaking adjustments.

92. Nov 13, 2007 | 10:21 pm

    Bogo wrote:

    Almost all of these explanations are wrong or miss the point. The force that causes the wire to rotate is called the Lorentz force. The magnetic field is in the axial direction of the magnet, and the charge flows radially. From F = qv x B, the direction of the force is perpendicular to both, in this case tangential to the surface of the magnet.

93. Nov 18, 2007 | 1:25 pm

    Cool Hand ASH wrote:

    Love it, will it go the opposite direction in the Southern Hemisphere??

    ASH

94. Dec 11, 2007 | 7:40 am

    aefer wrote:

    i just got my magnets in they are really strong but, don’t take the plastic diveders off the roll because there really hard to get them unstuck

95. Dec 16, 2007 | 4:39 pm

    RedArrow wrote:

    Anon. The whole key to this motor, or any electrical motor for that matter, is that the direction of the current has to be perpendicular to the direction of the magnetic field. I haven’t made or studied how a homopolar motor works specifically, but your classic electric motor has an armature (coiled copper wire) with a current run through it that is placed in a magnetic field. The equation for the force applied to the armature is F=ILB.
    F = force in newtons
    I = current in amps
    L = length of wire in the magnetic field in meters
    B = strength of the magnetic field in teslas

96. Dec 16, 2007 | 5:43 pm

    RedArrow wrote:

    also. i noticed some people talking about this generating power. its called a motor for a reason. it converts electrical energy into mechanical energy. in other words, this CONSUMES energy. now you could hook this up to the worlds smallest generator and it would convert the mechanical energy back into electrical energy. however, you would never be able to reclaim all of the energy because neither the motor, nor the generator is 100 percent efficient.

97. Dec 16, 2007 | 5:48 pm

    RedArrow wrote:

    and finally its time to crack on the stupid person. someone said you could charge the battery simply by spinning the wire in the opposite direction that it was trying to spin. wrong. all that does is stop the motor from SPINNING. it is actually still running when you are spinning it the other way.

98. Jan 8, 2008 | 12:12 pm

    CLM wrote:

    This was a fun project! Thanks for the great notes and ideas. Here are some of our notes to help those of you trying this for the first time:

    -We tried coax cable, but it was NOT made of solid copper, so it could not be used. We used a 20 gauge wire which worked fine but gets bent out of shape easily.

    -It took some time to bend the wire into the right shape. Start with trying to balance the wire on both sides of the magnet, then refine the shape. Remember that too much friction will prevent your wire from spinning.

    -A magnet form an old microwave works great with an inverted ‘C’ battery set into the hole. Since this type of magnet does not conduct, you need to strip off the battery’s label and clean off the glue residue. Then the copper wire should be positioned to touch the sides of the battery and NOT the magnet.

    -Beware, when the copper wire is not spinning, it gets VERY HOT. Use pliers to remove it from the system.

    Good luck!
    CLM

99. Jan 19, 2008 | 1:30 pm

    Ryan mondy wrote:

    can you use it to make things run?

100. Jan 28, 2008 | 6:09 pm

     Dangerously Fun wrote:

     @Ryan mondy:
     No. It is very inefficient. Batteries are good at powering things, but this is just a battery that is already powering something else.

101. Jan 29, 2008 | 5:41 pm

     Katie wrote:

     Neodymium magnets come in differnt strengths ie N35 N48 N52 etc. If you use a stronger magnet, will the wire spin faster?

102. Feb 8, 2008 | 10:55 pm

     Dangerously Fun wrote:

     @Katie:
     Yes, generally the stronger the magnet the more force will be exerted on the wire.

103. Feb 9, 2008 | 11:24 pm

     the him wrote:

     i tried this project for my science fair and i got an easy 100 u should try it

104. Feb 13, 2008 | 3:27 am

     elex freak wrote:

     Cool factoid: A new US Navy ship LHD-8 Makin Island has twin 5K HP variable speed Homopolar motors (Alstom USA) wound onto its propulsion shafts for diesel electric running at low speeds.

105. Feb 17, 2008 | 11:52 pm

     jj fish wrote:

     If I understand the magnetic rules correctly, the force is only against the parts of the wire that are perpendicular to the magnet, correct? Is the magnetic field induced through the battery also, so that the force acts on the top and bottom parts of the wire that are perpendicular to the field?

106. Feb 19, 2008 | 8:52 pm

     mhmhmhmhmhm wrote:

     Man! I’ve never needed so much patience in my life!

107. Feb 23, 2008 | 2:36 pm

     rob wrote:

     wow this is the coolest thing ive ever made!!!!!!!!!!!!!!

108. Feb 28, 2008 | 1:00 pm

     rosemary wrote:

     wohoo! im taking a introduction to micro-controllers class and learnd how to make a homopolar motor! now i will be making more shapes and learning more about how they work.

109. Mar 10, 2008 | 1:24 am

     vega wrote:

     working perfectly but bending the wire was a bit hard

110. Mar 12, 2008 | 2:59 pm

     javon wrote:

     works fine but cant get the wire to stay on the battery.

111. Apr 11, 2008 | 3:46 pm

     Sumguy wrote:

     To all with delusions of charging your batteries: Even if you spin it, you still have a dead short between the battery posts. How fast do you think you can spin it?!? How much energy do you think that would require?!? Any motor can be a generator if spun by an external force, but some are better than others.

     Still, this is the best fun I’ve ever had draining batteries!

112. Apr 12, 2008 | 8:39 pm

     all about us wrote:

     It took me awhile to get it to work, but when it did it was cool. It burns out the batteries really quick.

113. Apr 23, 2008 | 12:01 am

     tito wrote:

     “C” batteries work very well. I tried this yesterday with AA, AAA, C, and D and found that C works better than A’s but is easier to handle and create shapes with the wire. D’s are hard to use because the wire often knocks against the battery as it spins. The slightest friction can impede movement.

114. Apr 30, 2008 | 5:29 pm

     sciencedoc wrote:

     1. The chemical reaction in regular batteries is not reversable and you cannot charge them by spinning the wire.

     2. Current through a wire creates a magnetic field. Putting a magnetic field in a magnetic field will create magnetic repulsion which will cause the wire to rotate.

     This motor is a great example of magnetic fields. Putting a small dimple in the positice pole with a center punch will make it easier to keep the wire on the battery.

     Neodynium magnets work, ceramic magnets won’t get over it and buy them from the recommended online supplier or someone locally. Don’t get magnetic name tags, they’re too expensive that way.

115. May 8, 2008 | 1:46 pm

     dpfeldman wrote:

     The way this works is by field-current coupling. The current in the wire is being deflected by the magnetic field. The equation is F = q(v x B) where F is the force vector, q is the charge, v is the velocity of the charge and B is the magnetic field. The ‘x’ is the cross-product operator. Look this up in your high school physics book if you need to. Anyway, the magnetic field is vertical, and therefore the horizontal components of the current in the wire are deflected to the side, thus pushing the horizontal part of the wire to the side.

116. May 8, 2008 | 7:12 pm

     davea0511 wrote:

     Ha! I love it when people see something like this and think a free energy device has been created. I hear it with solar … let’s charge a solar cell with a lightbulb that’s powered by by the solar cell and generate free light forever! There are losses in all systems, people - that’s what heat is (the wire in this thing is roasting) - the conversion of electrical energy to heat energy is lost forever. This is a battery driving a motor … hook the motor up to charge another battery will never charge it as high as the original battery. It’s called the law of conservation.

117. May 16, 2008 | 7:16 pm

     davekeenan wrote:

     I’ve built upside-down versions of these where the wire is a tripod stand and the battery and magnet rotate, but what would be really cool is one where only the battery rotates. Can anyone do it?

     First requirement is a battery that won’t be attracted to the magnet. You can remove the steel outer shell from an old fashioned non-rechargeable zinc-acid-manganese-dioxide cell, and expose the zinc casing.

118. May 18, 2008 | 5:21 am

     Andrew wrote:

     A great little physics experiment. This page is quite popular. I’ve got to say that the change from a wide coil to a screw type coil makes for an interesting effect. Good as a trick to those who don’t know how the motor effect works.
     Blew the physics teacher away with this design.

     Thanks Dangerously Fun

119. May 18, 2008 | 10:18 am

     Tainted wrote:

     Hello q? .. if i hold it and spin it clockwise 3 times it spins back 3 times anticlockwise going back to the position it started… same for 2 turns or 4 turns it always goes back to where it was when i turned it.. im using a stack of magnets all stuck together and the middle 4 are repeling… is there a name for this and if there is what law/theroy does it come under… (school project -.-)

120. Jun 28, 2008 | 11:48 am

     bj wrote:

     i cant wait till i get to try this!

121. Jun 30, 2008 | 3:45 pm

     Munky Manz wrote:

     I did this at scouts a while back. its really fun and you should try it with a whole bunch of these going at a time

122. Jul 8, 2008 | 9:49 pm

     Mac Iver wrote:

     You can make it with only one contact on the magnet and the other though shorter one acting as a counterbalance still on top. Compared to the two contacts, this one will heat up slower or not as much in general.

123. Jul 9, 2008 | 12:49 pm

     ross freeman wrote:

     can i use a copper coat hanger?

124. Jul 16, 2008 | 3:02 pm

     JoebH. wrote:

     ive found a similar experiment where you attach the neomodium magnets to the end of a drywall screw, touch the screw point to the positive end of a c-cell battery (it should hang there because of the magnet) and touch wire to the - side of the battery and lightly to the disc magnet

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