SIMPLE ELECTRIC MOTOR

Length of Project:
Project theme:
Suitable for grades:
INSPIRATION
Electric motors work by applying electricity to a system of magnets and wires that results in a spinning motion. So long as the electricity comes from a sustainable source, electric motors don’t produce the same environmentally damaging emissions as internal combustion engines. As such, it provides an increasingly viable alternative to our reliance on fossil fuels to power our engines. Does moving a magnet around a wire create a measurable difference in current in the wire? How can this phenomenon be harnessed to produce electricity?

OBJECTIVE
Students will explore the variables that affect the rate of spin of a simple electric motor through designing, assembling, and testing their own small motors.

TRADES CONNECTION - TOOLS
Electricians, millwrights, plumbers, carpenters.

RESOURCE DOWNLOADS
Electrifying Math: Introduction and Glossary
Scientific Method Resource
Tools & Materials
Material List
  • ~25 cm of 18-22 AWG magnet wire (enamel wire)
  • Assorted gauges and types of wire for experimentation
  • One 9V battery
  • Assorted batteries for experimentation
  • Assorted magnets (i.e., neodymium magnets, rare earth magnets, etc.)
  • 2 connector wires with alligator clips
  • 1 mug or similar non-conductive container
  • 2 medium-sized binder clips
Tool list
  • Wire cutters
  • Sandpaper
  • Electrical tape
  • Smart phone or microphone with a computer, with a sound-recording software that provides decibels vs time graph (free options are available such as Audacity)

    • Optional:

  • Variable DC power source
  • Optical tachometer and reflective tape
Procedure

    Note: This procedure describes only ONE of the many designs that work – you may choose to offer students various wire, magnet, and battery options and let them experiment with which components work best for them, adapting the design as needed to accommodate different battery sizes, etc., including hooking their motors up to a variable DC power source.

  1. Wrap the magnet wire tightly at least three or more times around a D battery or any found cylindrical object to create your coil. Pull the coil off carefully and secure the ends at the 3 o’clock and 9 o’clock positions by making a few tight wraps to bundle the coiled wire or by wrapping tightly with electrical tape. Make sure to leave about 3cm of wire extending from each side.
  2. Make the wire ends poke directly away from the coil – this makes the axle for the coil spin around.
  3. Use the sandpaper to scrape away the coating from ONE of the 3cm arms. Then, scrape the coating off ONLY the top of the second arm, leaving one long length of coating on the bottom of the arm. This will create an electrical barrier that stops the electrical current for a brief moment every time the coil spins around, allowing the coil to keep spinning on its momentum instead of getting stuck in one position.
  4. Clip the binder clips to the top rim of the mug, then lay the mug on its side with the mouth facing you.
  5. Place the coil arms into the inner binder clip wings, so the coil is suspended between them.
  6. Place the magnet(s) under the coil, adjusting the binder clip height until the coil clearance is less than 0.5cm (or your desired height).
  7. Use the connector wires to connect the outer binder clip wings to the battery terminals, then push the coil to help it start spinning.
  8. Use a sound analyzing program or app, such as “Audacity,” to record the sound of your motor. You may need to use a microphone if the sound peaks don’t show up well on the graph. Look at the time vs decibels readout and highlight the time between peaks of noise; this is the time for one revolution (in “seconds per revolution”). 60 divided by this number will give you the RPM of your motor. Note: let’s say you calculated your RPM to be 500. To get an idea of whether that value is at all accurate, you can search online “what does 500 BPM (beats per minute) sound like?”, then use your ears to compare that beat to the sound of your simple motor.

    9. TROUBLESHOOTING:

  9. Check your battery’s voltage with the multimeter to make sure it is charged.
  10. Did you strip the enamel coating off the top of only one wire and entirely off the other?
  11. Is the coil well balanced and able to spin freely? (I.e., are the wires pointing perfectly straight out on opposite sides?)
  12. Is it not spinning? Try the following: a stronger magnet, a stack of magnets, turning your magnets upside down, raising the magnets or lowering your binger clip.
  13. Is it spinning too violently? Try increasing the distance between the coil and the magnet.
  14. Is the motor spinning too quietly to be analyzed by the sound app? Try adding an active buzzer to the circuit or a more sensitive mic. Is there any other way you can think of to make your motor noisier?
  15. Does the additional resistance of the buzzer stop the coil from spinning? Try adding more voltage or add your buzzer quickly and take your reading immediately before the motor loses momentum.
Extension Challenges
  1. Design an alternative method to measure the RPM of the simple motor. Keep in mind that the electricity stops briefly every time the insulated (coated) section of the magnet wire touches the binder clip. Is there a device that could be inserted into this circuit that would indicate when electricity was and was not flowing? What tool can you use to detect the frequency this device is operating at?
  2. Take apart an electric motor in a broken drill, printer, blender, laptop, etc. Pay close attention to the parts as you remove them to draw the pieces in an “exploded diagram” fashion. Label as many parts as possible by looking at a user manual for that (or a similar) motor.
  3. Using the otimization example, design your own optimization problem and have your classmates solve it.
  4. Research the history of electric motors. What source of energy did early inventors use to produce electricity? Build a demo of an early electric motor to present to the class.
  5. Using a variable speed motor, such as a power drill, play with increasing and decreasing the RPM to make it “play” a song. See if your classmates can guess the song. What mechanism inside the motor allows the RPM to be varied with such precision?
  6. Design, draw the plans for and build three attachments that could be built onto this motor that would do some sort of work (i.e., an air fan, or a small winch to pull something across a table, or a noise maker, etc.)
  7. Draw a flip book that animates the construction process of this simple motor.
  8. Hold a “Students teach students” class. Students or partners draw the following questions out of a hat, research the answer, and do a 3-minute presentation to the class to explain their findings:
  9. What are the three similarities and three differences between DC and AC electric motors?
  10. What are the function of “brushes” in some electric motors?
  11. What are two unique characteristics of “stepper” motors, and what kinds of applications are these motors used for?
  12. Are electric motors better for the environment than internal combustion engines? Give two reasons why you could argue “yes” and two reasons why you could argue “no.”
  13. What is the limiting factor preventing electric motors from replacing all internal combustion engines? Find and summarize an article on recent research scientists are doing to overcome this challenge.
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