Physics Dept. Demonstration Manual

DEM41.1 - Beakman's D.C. Motor

Objective:

To demonstrate a working electric motor.

 
Apparatus:  
  • D Cell Battery
  • Magnet
  • Copper Coil


 

Method:

Place the coil in the cradle formed by the right ends of the paper clips. You may have to give it a gentle push to get it started, but it should begin to spin rapidly. If it spins erratically, make sure that the tails on the coil are centered on the sides of the coil.

When the un-insulated parts of the coil make contact with the paper clips, current flows through the coil, making it into an electromagnet. Since magnets attract, the coil attempts to align itself with the ceramic magnet. However, when the coil turns to face the magnet, contact is broken (because the insulation on one tail is now preventing current flow). Inertia causes the coil to continue around. When the coil makes are nearly complete spin, contact is re-established and the process repeats. Technically (if you look up references on more complex motors), this motor is a single-pole pulse motor. More complex motors are created by using more than one coil and more complex set of brushes (the things that connect the coils to the current) so that no matter where the coil is in the spin pattern, at least one coil is always energized and trying to turn the coil assembly to align with the next magnet. This motor is, I believe, the simplest motor design which retains the basic concept of more complex motors.