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Make your own simple motor!

  • Introduction
  • Results & Video
  • Materials
  • Procedure
  • Preparation & References
  • Downloads

In this activity, students will build their own motor using a AA battery, 2 safety pins, tape, some magnet wire and a small neodymium magnet. It's a very simple way to illustrate one of the great advances in the design of motors and it has the "wow" factor when students see that they can create motion using these simple components. Students can flip the magnet, change electrodes or rotate the coil and see how the direction of rotation is changed.

DC Motors

A simple design for a DC motor makes use of the force created when a magnetic field is oriented perpendicular to an electric field. Because the DC current runs in opposite directions at the top and bottom of this coil, the force at the bottom of the coil is going into the page; whereas, at the top of the coil, the force pushes the coil out of the page. The direction of the force that causes the coil (armature) to spin is identified using the Right Hand Rule.

torque

righthand

Right-Hand Rule for the Resultant Force

  1. Stretch your thumb out at a right angle from the fingers on your right hand.
  2. Point your thumb in the direction of the current (I)
  3. Point your fingers in line with the of the North pole of the magnet (B).
  4. The palm of your hand will open to the direction of Force created by the interaction of the 2 fields.

 

 

 

 

Video

This simple motor takes just a few minutes to put together if you have the right materials.

Setup

Design details. The armature is the finicky piece of the construction.

  • The ends must extend 180 degrees from each other across the circle to form a straight line.
  • The ends of the wire should conduct electricity on one side and be insulated on the other.
  • Tape is used to form a tight coil and to balance the weight of each side of the loops.
  • The ends of the wire should extend beyond the safety pins by a half inch to one inch so that it doesn't slide out easily.

armaturemotor carriage

Materials (for 1 motor)

  • 1.2 cm neodymium magnet
  • AA 1.5 V battery
  • 38 cm (15 inches) of 18 -20 gauge magnet wire,
    have also used 18 gauge solid (not stranded) insulated wire
  • wire stripper (if using insulated wire)
  • nail polish
  • black sharpie pen
  • tape
  • 4 cm long safety pins (Quilting Size 2)

 

Procedure:

Making the Armature

  1. Take a piece of the wire and wind it around the diameter of the AA battery 5-8 times, leaving a couple inches of wire at each end. With insulated wire 4-5 times around is okay, more wrapping will make the coil a bit too thick. For the magnet wire, it should be okay to wrap more times around the battery.

  2. The ends of the wire need to be at exact opposite ends of the circle being made, and should form a straight line with each other, so the axle of the armiture is flat.

  3. Wrap tape or wire through the donut hole to hold the coils tight together. If the coil hangs more heavily to one side, you can use the tape/wire to balance the weight as well.

  4. Create ends of the wire that conduct on one side and insulate on the other.
    Insulated wire - Strip the ends from the coil outward of the insulation. Then hold the straight ends of the wire at the edge of table, such that the plane of the coil is perpendicular to the plane of the table. Paint the top side of each end with nail polish and/or sharpie pen. Let it dry.

    Magnet wire - Hold the straight ends of the wire at the edge of the table, as described above and sand or scrape off the enamel coating on one side of the wire.

Assembling the electrodes, magnet and armiture support.

  1. Place the magnet on the side of the AA battery.
  2. Lay the battery down on the table with the magnet lying flat on top.
  3. Tape the opening side of the safety pins the electrodes on each side of the battery. Wrap a thick rubber band around to hold in place and to offer some insulation.
  4. Make sure that the height of the pins are such that when the coil ends are threaded through the safety pins, the coil hangs close to the battery but doesn't touch when spinning. Make sure that the height of the pins are also level.
  5. Make sure that the nail polish is dry and that the coated ends of the wire are facing the same direction. Place the armiture in the holes of the safety pins and give it a tap to start spinning.

Notes & References

The motor is derived from a number of sources found via YOUTUBE and an adaptation from a slightly larger motor described at the San Francisco Exploratorium website called the Stripped Down Motor. This site does a good job of explaining the key features of the construction.

For our science night, we want every child to take home the motor, so we wanted to do it with fewer parts. We swapped paper clips for safety pins because we thought elementary school kids would have difficulty bending paper clips.

Magnet Selection
Small 1/2" neodymium magnets worked, but 1/2" ceramic magnets from Radio Shack (part # 64-1883) did not.

References for futher reading & watching

1) Video explanation of the construction and discussion of Faraday's rule

 

2) Lesson plan from Georgia Southern, describing how to build the DC motor and carefully describing the right-hand rule to determine the direction of the Force. (PDF).

Left Hand Rule explained at the National Magnet Lab

The Right Hand Rule described at the Exploratorium website.

Download Files