enter image description here

This is a simple motor made with a magnet, a battery and a copper coil. I am curious to know how can it be explained using physics. I know that the copper is diamagnetic but not enough that it can cause the coil to rotate. I want to know why the coil rotates as the current flows in it.

  • 1
    \$\begingroup\$ Have you tried googling DC motors? There really is a huge amount of resources out there without having to come here. \$\endgroup\$
    – jramsay42
    Mar 6, 2018 at 10:12
  • \$\begingroup\$ Thanks. I didn't know how to start reading about it. I will search about DC motors. \$\endgroup\$
    – user141242
    Mar 6, 2018 at 10:16

1 Answer 1


Flemings left hand (motor) rule: -

enter image description here

If you pass current through a wire in a magnetic field then a force is produced. That force pushes one side of the coil outwards and, due to that current travelling in the opposite direction in the other coil side, it is attracted thus the coil turns. This happens because the current in the coil produces opposing and attracting magnetic fields.

However, it stops when aligned and this is not a motor as such. A DC motor requires a commutator to reverse the current at a certain mechanical angle so that the process repeats.

Picture source

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    \$\begingroup\$ I think that some of these motors rely on stripping the varnish off one side of the wire so that the "brushes" only conduct when the coil is "right-way-up". It only gets one helping push per revolution rather than two. It's not clear from the photo if this is the plan with this unit. \$\endgroup\$
    – Transistor
    Mar 6, 2018 at 10:32
  • \$\begingroup\$ @Transistor so inertia carries it through yes? \$\endgroup\$
    – Andy aka
    Mar 6, 2018 at 10:33
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    \$\begingroup\$ @transistor - you are right. I made this motor when I was in school. Essentially one end of wire of fully stripped off. However second end is half stripped so that during rotation, the circuit disconnects for half rotation. This ensures continuous rotation. Otherwise the coil would stop at an angle from the magnet. \$\endgroup\$ Mar 6, 2018 at 10:42
  • \$\begingroup\$ I'm not convinced from the poor picture whether this is an actual coil but rather a simple ring. \$\endgroup\$
    – Trevor_G
    Mar 6, 2018 at 16:19
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    \$\begingroup\$ @Trevor_G Busts bubble. Relevant Link \$\endgroup\$ Mar 6, 2018 at 16:48

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