Frank Thompson

Complex Permittivity of Solid, Liquid and Granular Materials using a four layer boundary cell

The four boundary cell is an important arrangement for the measurement of complex permittivity of bulk solids and liquids. Transcendental equations for reflection and transmission are derived and previous errors in the literature are noted. This measurement method is extended to granular samples where a compression technique is introduced to minimize the dispersion in S-parameter measurements associated with interface problems.

Microwave based wheat grain kernel characterisation

A low-cost microwave source and detector is designed to drive a microwave cylindrical cavity to determine the wet mass and moisture content of single wheat grain kernels. Differences in wet mass and moisture content can be distinguished from the changes in resonant frequency and attenuation. Moisture content (8% to 16%) of single wheat grain kernels was measured. Experimental results are presented and the calibration equations are implemented in a microcontroller. Wet mass and moisture content are shown on an LCD display on the microcontroller. The measurement procedure and evaluation of the system are presented in the proposed paper.

An experiment on the dispersion of light

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 measurements has been given in the conclusions.

Non-invasive measurement of lipid and water in single wheat grains using magnetic resonance imaging

In this paper, we used the magnetic resonance imaging (MRI) technique to image moisture and lipid oil distribution in a single wheat grain kernel. Spatial information on both oil and water distribution of 10% and 20% moisture content grain kernels is presented. 2D cut-plane images indicate that the lipid oil is mainly concentrated in the germ region and the outer epidermis layer, whereas, the moisture content (MC) is evenly distributed through the cross sectional area of the wheat grain. The results also show that for lower moisture contents, the MR images are dominated by the lipid signals opposed to the water, which is attributed to the differences in T/sub 2/ relaxation behaviour.

Dusting off the Lecher lines

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 is measured.

Waste not, want not

Sadly, modern society has developed very wasteful habits over the last few decades: consumer products, food and energy are perphaps waste items that are most obvious. Attempting to show how we can counteract wasteful habits, this article (a) makes reference to Helen Czerski in her efforts to stop her cycle from rusting away; and (b) shows how a relatively simple task can give new life to a domestic toaster.

An old flame

Flames are seen more often in chemistry than in physics laboratories. However, as a continuation of the previous colourful demonstration of a levitating Bunsen flame described recently in this journal (De Carvalho 2012 Phys Educ. 47 517), two short experiments are reported. Firstly, flame rectification is investigated and secondly, the electrical potential around a charged object is measured.

An electronic electroscope

An electronic electroscope has been constructed to update the design of a similar instrument reported in Physics Education several decades ago. The presence of positive or negative charges is easily distinguished with this electroscope and an experiment with a Faraday cup is carried out to show how easy it is to record the accumulation of charge with time.

Measuring heart beats

A simple instrument has been constructed to measure heart beats via an earlobe sensor. The pulse rate is determined from a Picoscope trace and pupils may wish to see how this rate changes after modest exertion.

Coupled Coils, Magnets and Lenz's Law.

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.