Electric Motors are used in so many real-world applications.  In fact, you can see them being used in household items such as fans, refrigerators, washing machines and vacuum cleaners.   An electric motor uses electrical energy to produce mechanical energy, while a generator (or dynamo) uses mechanical energy to produce electrical energy.  Let’s build a simple motor to understand the basic science principles behind it.

What do you need?

• 3 feet of magnet 22-gauge wire (Radio Shack catalog # 278-1345)
• 2 field magnets (Radio Shack Catalog # 64-1888)
• 2 jumbo size (2-inch) paper clips
• D-cell battery
• D-cell battery holder
• Knife

Instructions

• Step 1 – Prepare the coil using the wire
• This is the part of the motor that moves. Starting about 3 inches from the end of the wire, wrap it 25-30 times around a AAA battery to form a coil.  Leave the tail about 3 inches long on each end.
• Now carefully pull the coil off of the form, holding the wire so it doesn’t spring out of shape.
• To make the coil hold its shape permanently, we will wrap each free end of the wire around the coil a couple of times, making sure that the new binding turns are exactly opposite each other, so the coil can turn easily on the axis formed
  by the two free ends of wire, like a wheel
• If this method of holding the coil together is too difficult, feel free to use scotch tape or electrical tape to do the job. The important thing is to keep the coil together, and to have the two ends of the wire anchored well, and aligned
  in a straight line, so they form a good axle.
• Step 2 – Remove top half of the insulation from the tail ends of the coil
• It’s a small and subtle trick that makes the motor work. Hold the coil at the edge of a table, so the coil is straight up and down (not flat on the table), and one of the free wire ends is lying flat on the table.
• With a sharp knife, remove the top half of the insulation from the tail end.   Be careful to leave the bottom half of the wire with the enamel insulation intact.
• The top half of the wire will be shiny bare copper, and the bottom half will be the color of the insulation.
• Do the same thing to the other tail end, making sure the shiny bare copper side is facing up on both wire ends
• Step 3 – Prepare support for the coil
  • Straighten the larger loop of each paper clip.  This will form the support for the coil.
  • Hold one support to each end of the D cell.  This is done so electricity can flow from one support into the coil and back through other support to the battery. But this will only happen when the bare half of the wire is facing down, touching the supports. When the bare copper half is facing up, the insulated half is touching the supports, and no current can flow.
• Step 4 – Insert battery in the base, connect supports and attach the coil
  • We will use the battery holder to hold the battery.
  • Attach the supports to the holes in the plastics at the end.
  • Insert the battery into the holder.
  • Set the coil tail ends in the paper clip support.
  • Place the magnet on top of the battery holder just underneath the coil. Make sure the coil can still spin freely, and that it just misses the magnet.    Adjust the coil so it spins close to, but doesn’t touch, the magnet.  Adjust the
    coil and the clips until the coil stays balanced and centered while spinning freely on the clips. Good balance is important in getting the motor to operate well.
  • Place a strip of paper between the battery and the electrical contact in the holder.  This is the on/off switch. Remove
    the paper to allow electricity to flow into the motor, and replace the paper when you want to stop the motor and save the battery.
• Step 5 – Start the motor
• Remove the paper
• Give the coil a gentle push to get it going.
• You have succeeded if the coil spins by itself for 10 seconds.  If it doesn’t start, try spinning it in the other direction. The motor will only spin in one direction.

What’s happening?

An electric motor uses electrical energy to produce movement or mechanical energy.  The key to understanding the electric motor is to know how electric current behaves in a magnetic field.  The operative principle in an electric motor is the same as an
electromagnet.

Electricity is created when particles become charged.  Some are negatively charged (electrons), some are positively charted (protons) and others have no charge (neutrons).  The opposite charges attract, while particles with similar charges repel each other.  Combining electricity with magnets makes an electric motor.  An electric current in a magnetic field will experience a force.

What makes a motor turn is based on the fact that magnetic fields produce physical force that can move things. If you have
ever played with magnets you have seen this in action as you use one magnet to attract another magnet or force it to move without touching it, depending on how you line up their poles. All magnets have a north pole and a south pole. Like poles repel each other and unlike poles attract each other.  So, in a motor, electricity is used to create magnetic fields that oppose each other and cause something to move.  For a detailed explanation, see How does an
electric motor work.

Why does your hair stand on end at the Van de Graaff generator in the Museum?

The Museum’s Van de Graaff generator removes electrons from the large globe, giving it a high positive charge. If you stand on an
insulated plate and touch this globe, all parts of your body become positively charged, including your hair. Since like charges repel, every hair on your head is now trying to get away from every other hair. The best way is to stand straight up. Result – flyaway hairdo!

Resources

• http://www.deltasee.org/CTC/Activity%2011%20Build%20It%20Electric%20Motor.pdf
• http://scitoys.com/scitoys/scitoys/electro/electro4.html#franklin
• http://scitoys.com/scitoys/scitoys/electro/railgun/railgun.html