This video is part of a little series of videos I'm making on handling neodymium magnets safely. In this video I will show you how to determine the poles on disc, cube and sphere magnets. Knowing your magnets polarity is very useful for safely combining large magnets as shown in one of my other videos in this series.

Music is by Kevin MacLeod (from his website incompetech.com) and Nick van Man (from his website music4yourvids.co.uk) used under Creative Commons license. Tracks used:

0:00 - 0:06 'Supernatural' by Kevin MacLeod
ISRC: USUAN1100397

0:06 - 5:40 'Watching the sun go down' by Rick Van Man

Here are the captions in case you don't understand my Danish accent:
- Hi. In an earlier video I showed the advantages of knowing the polarities of your magnets. In this video I'm gonna show you how to determine the polarities of your magnets. Where is the north pole?
- The professional way is to buy a dedicated pole detector. With just a click on a button it will tell you whether it's a north pole or a south pole you are pointing towards.
- This is my favorite method. Use an old-school compass.
- Let's start with a disc magnet as these are the easiest to determine. The poles are on the large flat surfaces. I let the magnet stand on its side so the poles are pointing towards the compass. Now I spin the magnet until the south part of the compass needle - which is actually a small magnet in itself - points towards the disc magnet.
- With magnets opposite polarities attracts so now I know the north pole of my disc magnet is pointing towards the compass. I mark the north pole of the magnet with an N. And double check just for good measure. If I spin the magnet with no poles pointing towards the compass the needle doesn't move. This is valuable information for our next challenge: The cube magnet.
- On a cube magnet you can't tell by the naked eye on which two surfaces the poles are. So you just have to put it randomly down. In this case I was a little unlucky and put the magnet down with its sides pointing towards the compass. Because the compass needle is not spinning along with the magnet. Therefore the poles of the magnet must be on the top and bottom surfaces and I have to tilt the magnet 90 degrees. Now the poles are pointing towards the compass and I do exactly the same as with the disc magnet.
- With south pointing towards the magnet I have found the north pole of my magnet. Right here. I mark the north pole of the magnet with an N.
- And now for the real challenge: The sphere magnet. Where are the poles on this one?
- With a magnet that can roll in all directions it is very hard to get a steady and exact reading. The solution is to put the magnet on what I call a security board. This is just a thin wooden plate with a metal plate glued to the backside. On this board the magnet will always align with one pole pointing directly into the board and the other pole pointing directly upwards.
- By now you should have figured out how to find the north pole.
- The final method I am going to show you is to use the magnet as a compass in itself. In this case I'm going to use two small magnets from a play set. By hanging them on a long tension-free line the magnets will act as a compass and align with the Earth's magnetic field. I cannot force them to point in another direction. Eventually they will stop pointing in the same direction everytime. Make sure there is not metal close by - just like when you use a compass.
- Here I point towards the geographic north. By definition the north pole of a magnet is the pole pointing towards the geographic north so northpole on a magnet is short for northpointing pole. That means I can mark the pole pointing towards north as the north pole.
- Another version of this method is to float the magnet on some styrofoam in the middle of a waterbath. It takes a little more preparation but has much faster response time as shown.
- Once you have determined the polarities of one magnet you can use it to determine it on all other magnets. The south pole of the marked magnet will stick to the north pole of your unmarked magnet.