Question: How do you measure a magnets strength?

Alex Bainbridge answered on 10 Mar 2022:

Great question! There are a few different ways we typically do it, which one is best depends on the strength and shape of the magnet and what exactly we want to know!

The most common is to use a a device called a Hall probe, which is a little semiconductor about the thickness of a hair, which you put an electric current though and it will produce a voltage you can measure depending on how strong the field is.

Another is to use nuclear magnetic resonance which is complicated. We wrap a coil of wire around a vial of water inside the magnetic field, and pass a high frequency alternating current through the wire. At a certain frequency, that depends on how strong the magnetic field is, the hydrogen nuclei in the water will suddenly flip over which changes the voltage in the coil of wire.

We can also measure the the total field along the length of the magnet by stretching a wire through it and moving the wire. A moving wire in a magnetic field generates a voltage which you can measure, and if you know how fast the wire is moving and the length of the wire inside the field you can use these to work out the field strength!