The magnetization of a ferromagnetic substance occurs in little jumps as the magnetic moments of small bunches of atoms, called domains, align themselves with the external field. We can actually "hear" the switching of these domains by amplifying the currents induced in a coil that surround the ferromagnetic material.
How it works:
We use two 10mH coils mounted back-to-back to cut out AC noise. The samples, listed in Fig.1 are in wire form, about 3-5cm in length and pushed through corks so they can sit...
Stable levitation of one magnet by another is usually prohibited by Earnshaw's Theorem, but the introduction of diamagnetic material at special locations can stabilize such levitation. The demonstration is a replica of an experiment described by M.D. Simon and A.K. Geim1 and is pictured in the photograph. The illustration is from their paper.
The behavior of a substance in a non-uniform magnetic field will depend upon whether it is ferromagnetic, paramagnetic or diamagnetic. Here we test different substances to see how they are influenced by a magnetic field.
How it works:
We have a collection of samples (listed in table 1) that exhibit well the three magnetic properties. Diamagnetic substances have a negative relative permeability (susceptibility); paramagnetic substances have positive.
A 60 Hz AC magnetic flux from an iron core induces an emf in a suspended coil of wire. With appropriate capacitance added, the coil will be attracted to, repelled from, or not affected by the magnetic flux.
Observe the induced current in a gimbaled coil as it rotates in Earth's magnetic field.
What it Shows
A changing magnetic flux through a circular coil of wire induces a current in the wire. By spinning a circular coil of wire at constant frequency and measuring the induced voltage across its ends we can find the local direction and magnitude of the Earth's magnetic field as it passes through the coil. The commutators of the coil are configured to produce an alternating current.
Image on black and white television is deflected by a magnet, not unlike the Maltese Cross.
What it shows: The television is basically a sophisticated cathode ray tube. The electron beam in the TV is influenced by magnetic fields in the same way as in Crookes tubes.
How it works: The image on a black & white TV is formed by a single electron gun scanning the screen. Holding a strong magnet to the side or in front of the screen deflects the beam from its regular sweep pattern, distorting the image.