John R. Reitz

Force on a Rectangular Coil Moving above a Conducting Slab

The force on a rectangular current‐carrying coil moving above and parallel to a conducting plate of arbitrary thickness is investigated. Expressions are developed for the lift and drag forces on the coil as a function of speed. Numerical calculations are made for a very thick plate and for plates with thickness of the order of the skin depth. Thick‐plate results are compared with experimental measurements of lift and drag on a superconducting coil suspended above a rotating aluminum wheel.

Eddy Currents in Finite Conducting Sheets

This paper deals with eddy currents in bounded plane conductors. Specifically, we are concerned with the semi‐infinite plane sheet and a conducting disk. The eddy‐current distribution in a perfectly conducting sheet or disk due to a magnetic monopole source is obtained by a technique due to Sommerfeld. Sommerfelds analysis for the disk is incomplete, but we have completed the derivation for this geometry. The eddy‐current decay in a semi‐infinite sheet of finite conductivity is solved by an approximate technique. The results are used to calculate lift, drag, and transverse forces on a magnetic monopole moving parallel to the edge of a semi‐infinite sheet of finite conductivity.

High-speed transportation via magnetically supported vehicles. A study of the magnetic forces

THE PARAMETERS AFFECTING THE MAGNETIC BUOYANCY AND RESISTANCE FORCES WERE ANALYZED FOR A VEHICLE EQUIPPED WITH SUPPORTING MAGNETS WHICH IS SUSPENDED ON A CONDUCTING TRACK-BED. IN PARTICULAR THE EFFECT OF A TRACK-BED OF FINITE WIDTH WAS INVESTIGATED. THE MEASUREMENTS EXTENDED TO THE FORCES ACTING ON A PERMANENTLY EXCITED SUPERCONDUCTING COIL, THE COIL BEING SUSPENDED OVER A ROTATING ALUMINIUM WHEEL WITH PERIPHERAL SPEEDS UP TO 480 KM/H. CALCULATIONS AND MEASUREMENTS SHOWED THAT THE IMPORTANT PARAMETER IS THE REYNOLDS NUMBER LAMBA = VH (MU) (SIGMA), WHERE MU AND SIGMA REPRESENT THE PERMEABILITY AND CONDUCTIVITY OF THE TRACK-BED, V THE VELOCITY OF THE VEHICLE AND H THE OPERATIONAL HEIGHT OF THE MAGNET OF THE VEHICLE. THE EFFICIENCY OF THE SYSTEM, EXPRESSED AS THE RATIO OF THE BUOYANCY TO THE RESISTANCE, IS PROPORTIONAL TO THE SQUARE ROOT OF LAMBA. /TR/

Theory of spin wave spectra in Heusler alloys

The spin wave spectra of three Heusler alloys (X2MnZ) measured by Ishikawa et al have been analysed by means of a model containing the three magnetic interactions which we believe are present in these materials: Coulomb exchange between localized dl and itinerant di electrons, s‐dl exchange, and superexchange via the Z atoms. Reasonable fits to the data were obtained in which the main variation between alloys was a differing di‐dl interaction representing the change in di electron density as X is varied. This di‐dl interaction dominates the first three near‐neighbor exchange parameters and appears to be responsible for ferromagnetism in these alloys.

Physics and the car business

Physicists have made important contributions to many areas of Ford Motor Company activity, particularly in areas of basic and applied research and product development. A number have assumed positions with management responsibility. Many of the technical problems facing the automotive industry today require a fundamental understanding, and the ability of physicists to contribute to the solution of these problems is greater now than it has been in the past. The present paper discusses some of these problems, and also traces a few case histories of physicists at Ford Motor Company; these illustrate the wide diversity of career paths for persons entering industry with a physics background.

Potential for energy savings in old and new auto engines

This paper disucsses the potential for energy savings in the transportation sector through the use of both improved and entirely new automotive engines. Although spark‐ignition and diesel internal combustion engines will remain the dominant choices for passenger‐car use throughout the rest of this century, improved versions of these engines (lean‐burn, low‐friction spark‐ignition and adiabatic, low‐friction diesel engines) could, in the long term, provide a 20–30 percent improvement in fuel economy over what is currently available. The use of new materials, and modifications to both vehicle structure and vehicle transmissions may yield further improvements. Over a longer time frame, the introduction of the high‐temperature gas‐turbine engine and the use of new synfuels may provide further opportunities for energy conservation.

Magnetic Forces on a Coil Moving Above a Conducting Plate

Magnetic levitation is one of the more promising methods suggested for supporting high‐speed vehicles; high‐field‐strength magnets or coils in the vehicle are to be levitated by magnetic fields resulting from eddy currents induced in the conducting roadbed or guideway. In the present study the forces on a rectangular, flat, current‐carrying coil moving above and parallel to a conducting plate of arbitrary thickness are investigated. Analytical expressions are developed for the lift and drag forces on the coil as a function of speed. Numerical calculations are carried out for a very thick plate and for a plate with thickness of the order of the skin depth. Thick plate results are compared with experimental measurements of lift and drag on a superconducting coil suspended above a rotating aluminum wheel.