The Foucault current
Coils, solenoids and other things
Measurement of a magnetic field
Magnetic properties of materials
And if there's no variation in flow?
The rotating magnetic field
High frequency fields
INTERACTIVE EXPERIMENTS AND EXHIBITS
To begin with, a curiosity::
A thin (ferromagnetic) iron pipe is placed so that it can run up and down a guide. It spontaneously goes to the area of maximum intensity of the magnetic field which for a ring magnet is evidently not on the plane of the ringís surface, but slightly above it.
Now letís study the forces between magnets and different materials.
Now letís see two experiments in which we measure the force that a magnet exerts on two materials having quite different magnetic properties. We use an analytical scale to the milligram. In the foreground a small graphite cylinder, a pure aluminium rod and a powerful samarium-cobalt magnet. On the right plate we have placed a light plastic glass upside-down, the purpose of which is to keep the graphite sample away from the plate which, although made of brass, is galvanized so it can be attracted by a magnetic force.
A force of repulsion of some ten milligrams is evident. The graphite is diamagnetic!
And now an experiment in which we show what force a magnet exerts on pure aluminium.
We have not repeated the experiment with a ferromagnetic material since the forces in play are far greater and it is a common experience to see the strong attraction a magnet exerts on a piece of iron, nickel, chrome and so on.