It is a well known fact that the Earth carries a net negative charge that produces a downward electrostatic field. The present experiment shows how this field can be measured with a Field Mill which has been constructed from components readily available in the Laboratory. In fine weather conditions a value of 120 (±10) V m[superscript -1] was…

An absorption line at 900 nm has been observed in Perspex. Samples of 1 and 2 cm thickness were used and the integrated absorption (line width times peak absorption) of the line was proportionate to the thickness. Facilities for lowering the sample temperature were not available and therefore both measurements were carried out at room temperature.…

Most people are familiar with arc discharges through the use of simple gas lighters within the home but corona discharges are not so common. This note presents students with three simple corona discharge experiments so that they can appreciate this form of electrical discharge. Firstly, one detects whether positive or negative ions are created;…

Resonant cavity perturbation as a means to measuring permittivity has been used since the early 1940s. It is attractive because it is non-contact, non-destructive and experimentally simple. Only recently, however, has the cost of a small analyser board become acceptably low that experiments can be carried out in schools and colleges. Using the TE…

Experiments with Lecher Lines have always been important in the physics curriculum for demonstrating standing waves and the important concept that waves can be guided as well as being emitted into space. A system operating at low power (less than 10 mW) and in the frequency range 300 MHz to 800MHz is described and the wavelength of the radiation…

A simplified theoretical explanation of dispersion in dielectric materials has been given and experiments have been carried out on two liquids, namely, distilled water and sunflower oil. The appendix contains a detailed description of the construction of a homemade spectrometer and hollow prism and an assessment of its suitability for the above…

Paramagnetic and diamagnetic materials are now generally known as the "Cinderella" materials of the magnetic world. However, susceptibility measurements made on these materials in the past have revealed many details about the molecular bonding and the atomic structure of the so-called "transition" elements. Indeed, the magnetic moment of neodymium…

One of the basic truths regarding energy conversion is that no thermodynamic cycle can be devised that is more efficient than a Carnot cycle operating between the same temperature limits. The efficiency of the Stirling cycle (patented by Rev. Robert Stirling in 1816) can approach that of the Carnot cycle and yet has not had the commercial success…

Great scientists in the past have experimented with coils and magnets. Here we have a variation where coupling occurs between two coils and the oscillatory motion of two magnets to give somewhat surprising results. (Contains 6 figures and 1 footnote.)

A recent article showed how the influx of neodymium magnets has provided striking demonstrations of the interactions between magnets and conductors. The "shaking torch" is yet another example. Many of these torches require no batteries and can be submerged in water--indeed, a light for life. In this article, the author disassembles a shaking torch…

Archimedes (287-212 BC) is well known for his explanation of buoyancy, and in particular for his "eureka" moment. This experiment uses his density measurement method to find the purity of gold, and additional confirmation of the findings are given by x-ray fluorescence. (Contains 4 figures and 1 table.)

Measurement of the level of a liquid is needed in many hydrodynamic situations. In the present article, this has been achieved with a conductivity sensor for the specific case of water levels. The use of this system is illustrated by the automation of a gasometer in which the gas is collected in an inverted measuring cylinder resting in a water…