More Questions on Electro-Magnets

[murphyslabrat]

Okay, so winding 60 feet of 37-awg on a half inch spool takes a long time. I want to know if I can fold the wire and wrap several strands at once. Would this affect the polarity or strength of the electro-magnet?

 

[silverpig]

Yes it most certainly does, and if you were to fold it and wrap the magnet you'd get no field as it would cancel itself out.

You can try using a drill or something else automated to do the spinning while you guide the wire.

 

[Mark R]

You could fold it, then cut the ends to get several seperate strands - then wrap those several strands at once.

You would have to connect it up correctly though, so that the end of one strand connects to the beginning of the other - the electrical current must flow the same direction through each twist (opposite twists will just cancel out).

Easiest way though is just to use a lathe or drill to spin your spool.

 

[Paperdoc]

Use the Left-Hand Rule. see LHR#2 on this Wiki page:

http://schools.wikia.com/wiki/Left_hand_rules

Use your LEFT and and wrap it around the winding you are making so that your finger tips point in the direction of CURRENT flow. Remember that the convention for Current is that it flows from positive to negative, not the reality of electron flow. Now the thumb of you left hand fist point to the NORTH pole of the electromagnet you've made.

To your original question, then suppose you fold the wire in half and wrap it around a core. Now imagine For the first half of the coil, the current flows in one direction. But at the end of the coil it suddenly reversed around the fold and stars flowing in the opposite direction in space. So the fields produced by the two halves of your coil cancel each other.

If you cut the wire into two pieces and wrap them in parallel around your core at the same time, you basically create two windings in parallel around a single core. Then what? Well, if you connect wire ends together so that they are operating in parallel electrically, then the two coils' fields reinforce each other and you still have an electromagnet. If you run an alternating current through ONE coil only and then connect a load across the ends of the other, you'll find current flowing through the load. You have just built a transformer!