Abstract:
The total magnetic energy of a solenoid can be reduced by the introduction of a magnetic material. This effect is exploited in the operation of actuators used in a variety of applications ranging from automobile door locks to the clamping of airplane landing gear. Ferrofluid[sup TM] is a stable colloidal suspension of magnetic particles in a liquid carrier with (mu)(less than or equal to)3(mu)[inf 0] and viscosities in the range from 10--6000 cp. A report will be made on a measurement of the resonant oscillations of the magnetically driven ferrofluid contained in a U-tube geometry. The ferrofluid ``plug'' functions as a double-acting piston which generates sound in the gas volumes which are above the fluid-free surface. [Work supported by the Office of Naval Research.]