As the title states, I need to measure the magnetic field strength on the surface of a neodymium magnet but I do not have access to a Gaussmeter.
Initially, I tried placing the magnet next to a compass so that the magnet's magnetic field is acting on the compass needle in a perpendicular direction to earth's magnetic field. Then, using the angle the needle is displaced from pointing north (and earth's known magnetic field), the magnet's magnetic field can be worked out. Of course, however, the magnet's magnetic field is much stronger than that of the earth, so, the compass needle pointed directly at the magnet.
To solve this, I decided to back the magnet up far enough that the compass needle is displaced by a lesser amount. As I was not sure exactly how the distance between the magnet and the compass needle changes the magnetic field strength (perhaps someone can clear this up?), I took a number of measurements of the angle displacement at different distances.
Making a plot revealed that the magnet's magnetic field strength is inversely proportional to the cube of the distance from the compass needle. This concerned me because at distance 0 (the surface of the magnet), the magnetic field strength is "infinite." Of course, this is incorrect but I am not sure where I have gone wrong. Could someone point out the flaw in my understanding and suggest how the experiment could be modified to find the magnetic field strength on the surface of the magnet (or an alternate better experiment)? Thanks.