Modelling and analysis of electrodynamic suspension of an aluminium disc as a complex engineering problem

A final year project is an effective tool in teaching complex engineering phenomena. Problem identification and formulation, applying mathematical and engineering knowledge for solving a problem, and design and synthesis of the final product are some of the outcomes that the students achieve upon completing such projects. In this paper, the design of an electrodynamic suspension system, in which an aluminium disc suspended above two concentric coils, is considered. The mathematical description is presented and proved that the value of electromagnetic force exerted on the disc is proportional to the inverse square of its height. The system is then simulated with a finite element method software and the effects of varying different system’s parameters on the exerted force are studied through simulation results. Analytical calculations and simulation results are validated by being compared with experimental measurements, which show a close agreement.

Levitation of an Aluminium Disc in a Magnetic Flux Well

An aluminium disc is levitated above a two-coil arrangement in a magnetic flux well, in a low voltage and wattage implementation. A coupled circuit analysis of the system allows an estimate of the lifting force.

Redeposition of Sputtered Material in a Glow-Discharge Lamp Measured by Means of an Ion Microprobe Mass Analyser

The redeposition of sputtered material on the target in a Grimm-type glow-discharge lamp was studied by means of an ion microprobe mass analyser (IMMA) using 16O2+ ions as bombarding species. The target was an aluminium disc with a cylindrical copper insertion, one mm in diameter. The lamp was operated at currents of 50 mA and 100 mA and a voltage of 1200 V. It is estimated that 17% of the copper atoms sputtered are redeposited and may be resputtered.

The infra-red secondary spectrum of hydrogen

The first observations of the "many lined" spectrum of hydrogen in the infra-red made by Croze, who measured the wave-lengths of 72 lines between 6838 Å. U. to the nearest on the Rowland system. Porlezza measured the wave-lengths of 43 lines between H a , though his plates were treated to record up to 8000 Å. U. Croze corrected some of his earlier lines and added some 27 more, but did not extend the further limit beyond 8027 Å. U., and his later results were still only given to the nearest integer. As Merton and Barratt had investigated the secondary spectrum only for wave-lengths less than H a , it was thought desirable to re-investigate the infra-red region, to obtain a more accurate record of the wave-lengths of the lines, and to push the limit, if possible, to longer wave-lengths. A plain diffraction grating spectroscope fitted with quartz lenses was used. The grating had 14,500 lines to the inch and gave a dispersion of 25 Å. per mm. An H-shaped vacumm-tube, fitted with aluminium disc electrodes at the heads of the upright stems, contained hydrogen, and to one stem of the tube a large glass bulb was sealed, so that a considerable volume of gas was available at about 2 mm. pressur. The capillary tube connecting the stems was 2 mm. internal diameter, and light emerging from the end of this tube parallel to the tube was directed on to the slit of the spectroscope with a quartz lens. In this "end-on" position the intensity of the secondary spectrum was at a maximum.

The attainment of high potentials by the use of radium

The original aim of the work described in this note was to measure the energy and numerical importance of each of the many distinct kinds of β -particles emitted by a single radioactive substance. Calculation of the energy of a β -particle from observation of its deflection in a magnetic field involves assumptions which are as yet insufficiently supported by experiment. Theoretically both the energies and distribution of the particles could be directly measured by giving a gradually increasing positive charge to the source of radiation; for, when the potential of the source is +V, electrons possessing energy less than e V will be drawn back to the source of radiation. Unfortunately, more than a million volts would be necessary to stop the fastest β -particles, and no method is at present known of maintaining such a high potential in vacuo . It was thought that this difficulty might possibly be overcome by using the active material itself in order to produce the high potential according to the principle employed in Strutt's radium clock. If the source of radiation were perfectly insulated its potential would rise until the swiftest β -particles could no longer escape. The present note deals with experiments made to test whether this method were practicable. It was found that high potentials were readily obtained, but the attempt to attain to a million volts tailed through the difficulties of insulation encountered. But few experiments were completed, and many failed as the result of accident. This shows that, even if perseverance had been rewarded by greater success, technical difficulties, accentuated by every effort to improve the insulation, would probably have prevented the practical application of the method. It seemed, therefore, useless to pursue the matter further, until more is known of the reasons why the insulation of a vacuum breaks down. In these experiments the source of β -radiation was 20 millicuries or more of purified radium emanation contained in a thin bulb—marked B in fig. 1—of about 1 cm. diameter. The bulb, which was just thick enough to stop all α -radiation, was supported by a fine silica rod R inside an exhausted glass flask F of 1 litre capacity. The rod, of diameter about 0⋅8 mm., was freshly drawn from transparent fused silica. The surface of the bulb and the flask was coated with silver, which was found to retain a trace of conductivity when subsequently heated to 400° C., though it then became almost transparent. The potential gained by the bulb was measured by a simple form of attracted disc electrometer, a circular aluminium disc being hung from the arm of a horizontal silica spring, the other end of which was soldered with aluminium to a projection from one of the glass walls of the flask. By observing with a microscope the. displacement of the disc, the force of attraction exerted on it by the bulb was measured, and from this it was easy to calculate the charge and the potential acquired by the bulb. The force of a dyne displaced the spring by about 0⋅1 mm. The disc was hung just at the entrance to the mouth of the flask, so that the remainder of the flask wall served the purpose of a guard-ring.