Electromagnets...

[Howard]

I have a little conumdrum on my hands... I wound two electromagnets with the same length of magnet wire around steel cores. One is 5" long, and the other 1.5". The 5" electromagnet seems much stronger than the 1.5" one, even though the field strength of an electromagnet is halved when the length is doubled?

I know that there are fewer turns on the 1.5" magnet because there are more layers (hence the radius grows faster than the 5"), but should this make so much difference?

It's 18 gauge copper magnet wire, btw.

 

[MacBaine]

It's sorcery!

 

[Howard]

Note: when I mean stronger, I mean picking objects up at the ends of the cores.

 

[ROTC1983]

Originally posted by: MacBaine
It's sorcery!

Burn him at the stake

 

[bigalt]

man this is digging really far into the dusty recesses of my memory, but i thought that the magnetic field inside a coil was directly proportional to the number of turns.

 

[Howard]

Originally posted by: bigalt
man this is digging really far into the dusty recesses of my memory, but i thought that the magnetic field inside a coil was directly proportional to the number of turns.

So, are you saying that the loss of magnetic field strength is because I have less turns?

 

[eLiu]

Originally posted by: bigalt
man this is digging really far into the dusty recesses of my memory, but i thought that the magnetic field inside a coil was directly proportional to the number of turns.

This is right...i just took the AP Physics C exam. B-field strength is more dependent on the number of turns than the radius. Especially since radius differs maybe by a few centimeters (the equations are worked with meters), while the number of turns is significantly bigger.

 

[Howard]

OK, I should have stayed with the longer electromagnet then.

I have some more questions... What is the best way to hand-wind an electromagnet using thin (24 or higher gauge) magnet wire? With thick wire it's easy... but I want my magnets to look professional, not haphazardly-wound.

Also, look at this image. There are lines of force between the unlike poles. The question is, if I put two bar-type electromagnets parallel to each other so that the north and south pole of each magnet are adjacent to the opposite pole of the other magnet, like this:

N...S
|....|
|....|
S...N

Will there be lines of force extending through the entire length of the magnets, or just at the tips? (where the letters are)

Thanks a bunch!

 

[Howard]

^

 

[dighn]

N...S
|....|
|....|
S...N

Will there be lines of force extending through the entire length of the magnets, or just at the tips? (where the letters are)

yes there will be lines of force extending through the entire length, ithink.

 

[Howard]

Originally posted by: dighn
yes there is

What question?

 

[Howard]

^