5K40.10 - DC Motors

Code Number:
Demo Title:
DC Motors
Design of DC Motor
Area of Study:
Electricity & Magnetism
Overhead DC Motor, Large DC Motor and Power Supply, Toy Motor with Fan, Small DC Motors (Assorted), 20 Volt DC Power Supply, Stripped Down DC Motor, 6 Volt Battery, Square Magnets (5 or 6), and Backwards Motors - Assorted.

Hook the Plexiglas motor up as shown.  Place on an overhead projector. Use no more than 15 Volts.  Be sure to align the arrows drawn on the motor to get correct armature and point placement.  The other set of arrows is where to place the rotating coils so that the motor will start when the voltage is applied.  This motor may also be hooked to one of the lecture bench galvanometers to show that it can also be a generator.  The large motor is hooked to its power supply and may be operated at variable rpms.  The smaller motors may be run off any DC power source as long as the voltage rating of each motor is not exceeded.

The small homemade motor is an easy one to use when trying to show motor direction verses magnetic field direction.  It can also be used to show rotation verses current direction.

The toy mobiles are nothing more than backwards motors.  In these motors the coil is the stationary part and the magnets are the rotating or moving part.

The "Lorentz Motor" attachment is designed for use in the Pasco adjustable magnets.  First screw the bolt insert into the magnet from the bottom up.  Then place the shaft of the attachment into the bolt insert and adjust the poles of the magnet so that they are about 3 mm from the coil when it is spinning.  Set the power supply for 12 Volts.  When it is running the coil will draw about 3 Amps.

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Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.