Teachspin - Magnetic Torque Instrument

Magnetic Torque - "A New Classic"

All Torque Measurements are done on a cue ball which has a magnetized disk imbedded at its center.

The handle is oriented along the direction of the magnetic moment.
The ball floats on an ultra low-friction bearing located at the center of the Helmholtz-like coils.

The electronics system is self contained.

The power supply has a DC current source for both the coils and the electronics for a strobe light and frequency counter.
The counter measures the rotational frequency of the spinning ball.
A compressed air source for the bearing is also included.

Force measurements are carried out on a magnetized disk supported in a gimbal.

A magnet, just like the one inside the ball, is set into a gimbal, a plastic holder free to rotate.
The gimbal is suspended from a spring which can be calibrated using the one gram steel spheres provided. (The spheres will adhere to the magnet.)
The power supply can be switched to make the currents in the two coils flow in opposite directions, creating a field gradient at the center of the coils.
The spring is suspended from a brass rod protruding from the plastic cap. The brass rod can be raised or lowered to return the gimbal to its initial position allowing for null measurements.

The spinning ball can be used to demonstrate a classical model of magnetic resonance, including the "spin-flip " that creates a spin echo.

A millitesla uniform magnetic field, created by permanent magnets and iron shims can be slipped over the air bearing.
Manually rotating the unit at the Larmor precession frequency of the spinning sphere visually demonstrates the "spin-flip" process.
While the rate of rotation is analogous to the Larmor frequency, the time of rotation models the pulse width of pulsed NMR.