# Finding the polarity of fridge magnets

1. Jun 22, 2009

### Firecoe

Hi guys.
Im reading on some magnetism and I thought, what is the polarity of a fridge magnet?
Does anyone have any ideas on how I might find out what the polarity of a fridge magnet is, ie what the field direction is?

2. Jun 22, 2009

### Born2bwire

Do you have a compass? That is pretty much the only standard you can compare against (well, you could use another magnet of known polarity) unless you want to mess around with currents and such. Is this question a purely academic exercise or a practical one? There are several ways you can determine the poles of a magnet. Another method is that you could create a solenoid and hook it up to an ammeter and see what direction the current flows when you insert/remove/drop the magnet through the solenoid. You could also hook up a current to the solenoid and make it an electromagnet (inserting an iron core for improved effect) and find the magnet's poles via attraction/repulsion.

3. Jun 22, 2009

### Staff: Mentor

I read somewhere that fridge magnets are actually composed of multiple strips of magnets, facing opposite directions. So they wouldn't have a polarity.

4. Jun 22, 2009

### Bob S

Use Born2bewire's suggestion: use a compass, and remember that the north-pointing end of the compass is a NORTH pole, and the magnetic pole near Greenland is a SOUTH pole.

5. Jun 27, 2009

### Firecoe

I see. thanks for the help guys. I just used Born2bewire's suggestion.

6. Jun 27, 2009

### Staff: Mentor

Did it work?

7. Jun 27, 2009

### ideasrule

Yup, that's true. Try this: slide one fridge magnet against another. Rotate the magnets with respect to each other and repeat. Do this until you feel "thud thud thud"; that happens because when you slide the magnets so that strips of the same polarity are on top of each other, the magnets repel and position themselves so that strips of opposite polarity are closer together.