Elementary split-ring armature DC motor. D+15+6 as a motor.

Elementary spit-ring armature DC motor. (Same as D+15+6 as a motor). A coil, free to rotate about a vertical axis, is mounted within a stationary magnetic field produced by two strong permanent bar magnets. Closing a knife switch sends current through the coil. The field produced by the coil swings the coil to line up with the permanent magnet field. However, just as the two fields become aligned, the coil 'split-ring' commutator causes the coil current and magnetic field to reverse, causing the coil to be repelled away from the bar magnets. The cycle then repeats, and the coil continues to revolve. The timer box beeps to alert the operator to turn off power to avoid burning up the motor.