Solinoid Construction: Bobbin Material and Rod Direction

[magnetic-man]

What is the best material to use for the bobbin (spool) to wind the copper wire around. I know plastic is used, but is aluminum any good for this? How do you determine which direction the rod will tavel through the coil without testing it first?

 

[mgb_phys]

The spool (the non moving part) doesn't really matter if it has no magnetic effect - you don't want to make it out of something more magnetisable than the moving part!

The right hand grip rule !

 

[LURCH]

Is the right hand rule needed for a solanoid? I mean, won't the rod will just try to center itself in the magnetic field? So, wherever you place the rod, and whicever way you wind the coil, and whichever way current is flowing, the rod will move toward the center of the coil, yes?

 

[mgb_phys]

If you change the direction of the current the iron bar will move in or out.
Remember the coil will magnetise the core