Direction of magnetic fields in solenoids (1 Viewer)

[helen888]

Hi,

I'm teaching myself Yr-11 level physics at the moment 'cause I'm planning to sit the GAMSAT next year... and I'm really stuck on how to work out the direction of the magnetic field in solenoids... as in which is the N and which is the S poles.

Can someone give me some help?

Thanks all

-helen

 

[zingerburger]

There are two ways to do it. This is the way I do it:

This requires a bit of spatial manipulation, so not everyone will be able to do it easily. Imagine rotating the solenoid around so that one end is facing you. Then imagine what direction the current would move in - clockwise or anti-clockwise. If the current moves anti-clockwise, it's a North pole. I remember it's a North because the word "anti-clockwise" has an "N" in it. Obviously, if it's clockwise, it's a South pole.

The other method might be easier. Say the diagram was a side-on view of the solenoid - you pretend to wrap your fingers around the coil so that your fingers point in the direction of the current. Your thumb will always point to the North pole.

And that's it. I hope that helps.

 

[dan.121212]

right hand thumb rule (look up weikipedia if u dunno how this simulates it)- applies for magnetic field around wire AND solenoid:

in wire, thumb simulates direction of current, and the way teh fingers are pointing is teh driection fo teh magnetic field, ie if a wire goes into page (represented by (x)) then mgnetic field is directed in a clockwise direction around that wire

in a solenoid, ur four fiingers represent teh direction of the current, and (as stated above) ur thumb represents the direction of the magnetic field and thus points to teh north pole

also hope trhat helps

 

[Nosviper]

It is quite easy, there are many methods to do it but just understanding the basics of magnetic fields and you will never forget it.

All you do is use Oersteads rule
1) Your four fingers curl in the direction of the current around the solenoid
2) Your thumb points to the left/right

You thumb is now pointing in the direction of the magnetic field. We all know magnetic files go out of the north and into the south. So if your thumb is pointing to the left that makes it north pole since the magnetic filed is leaving the solenoid and that and and entering on the other side.