# Magnetic field of magnet and its defination

1. Oct 25, 2012

### sgstudent

When we consider a magnet, usually we perceive the field lines to come out of the north pole. But since the poles of a magnet is actually just a man-defined thing, so actually the magnetic field doesn't emerge from the north but it's a constant loop. So when i draw the magnetic field of a bar magnet in this position, instinctively i will draw it like this: http://postimage.org/image/yzybv7vrl/full/ [Broken]

However if i invert my magnet then i would draw it like this:http://postimage.org/image/sh5ksynwt/full/ [Broken]

So if i take the north pole to be where the magnetic field emerges from, then the two magnetic field diagrams would be different but in actuality the second image should look similar to the first.

Thus, from this i'm confused about how i should draw my magnetic field diagram. Are there any guidelines so that i will draw the correct ones? Thanks for the help!

Last edited by a moderator: May 6, 2017
2. Oct 25, 2012

### AJ Bentley

I hate field lines too - fortunately they're not a very useful thing and you rarely see them being used except as a general indication of a field.

Anyway, the best way to look at is: If you bring a piece of iron near a pole, the pole will induce an opposite pole in the iron nearby. (it doesn't matter if it's a north or south pole)
Then that pole will induce another opposite pole in the iron as far away as it can. If it's a funny shape, it will induce several poles at the farthest points.

Once you've located all the induced poles, you can draw the field lines between them and add in any curves you feel might make it look more smooth.

3. Oct 26, 2012

### sgstudent

Haha we share the same pain. Field lines are so unpredictable. Your method really great! Thanks!

4. Oct 27, 2012

### sgstudent

Hello again. I was thinking about this and i thought what if both of the poles are exposed to the iron bar like this. Then how should i approach it? Should i draw both induced poles and from there draw the magnetic field? Something like this: http://postimage.org/image/5n2feusjf/full/ [Broken]

Thanks for the help!

Last edited by a moderator: May 6, 2017
5. Oct 27, 2012