Saturday, May 27, 2017


One of the kids' friends asked about magnets a few weeks ago.  This led to three weeks worth of play dates on electric circuits, electromagnets, and last but not least, Motors!!!  (It's nice to have a physicist in the family).

The motors were amazingly simple to put together, so I’m including the instructions.  Here’s a picture so we have something to talk about.

The parts are:
1 D cell battery
1 pound of 18 awg magnet wire, (you don’t need the whole pound, but Amazon sells It by the pound… seriously)
1 piece of cardboard out of the side of a box,
1 magnet
scotch tape

The How
Tape the D cell to the cardboard so it can’t move.  Next, cut two 4 inch pieces of magnet wire.  The next step is a bit of work, but use a kitchen knife, or a piece of sandpaper to scrape off the red insulation until you just see bare copper wire.  Place a dime size loop in one end of the wire, and then bend it over at a right angle to the rest of the wire to serve as a foot.  In the other end of the wire, make at least two pencil diameter loops to hold up the motor’s rotor, (the large coil of wire shown in the picture).  Tape the feet you made to the cardboard on either side of the battery, then tape the two wires to either side of the battery so that each of them is in contact with one of the poles, (the silver ends), of the battery.  Wrap the tape around a few times, and wrap it tight to make sure each wire is actually touching the pole.

Next, wrap magnet wire around the D cell to make the rotor coil.  Make about 10 turns.  This coil of wire is going to be the motor’s rotor, (a fancy name for the spinning bit).  Tie the ends of the wire through the loop so the loop can’t unravel, and leave about two inches of wire sticking out from opposite sides of the loop as shown in the picture.

Here’s the tricky bit.  Strip half the insulation off the pieces of wire sticking out from the coil.  Make the ends of the wire look like the diagram below.

If you strip off all the insulation, the motor won’t work.  The wire extending from the rotor needs to make electrical contact with the pencil diameter wire hoops attached to the battery only half the time.  It’ll spin through half a circle making electrical contact to the two posts you made earlier, and then during the next half circle it won’t.  Watch the wire on the left side of the rotor in the video . As it spins, you'll see that the side with insulation is visible, and then the side with bare metal.  (More on this in the ‘Why It Works’ section).

Now, insert the rotor into the pencil diameter hoops as shown in the picture.  Place the magnet on the battery pointed up at the rotor.  Then, give the rotor a little spin to get it moving, and it should spin happily around all on its own.

Next Time: Why it works

All the stuff for making motors:

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