The acoustical features of kettledrums have been analyzed by means of modal analysis and acoustic radiation (p/v ratio) measurements. Modal analysis of two different kettledrums was undertaken, exciting the system both by a hammer and a shaker. Up to 15 vibrational modes were clearly identified. Acoustic radiation was studied using two ways. Based on previous experiments of other researchers, a new parameter, called intensity of acoustic radiation (IAR), has been defined and measured. Results show a strict relationship between IAR and the frequency response function (FRF, which is the v/F ratio), and IAR also strongly relates the modal pattern to acoustic radiation. Finally, IAR is proposed for vibro-acoustical characterization of kettledrums and other musical instruments such as strings, pianos, and harpsichords.

Modal analysis and intensity of acoustic radiation of the kettledrum

We determine the solar constant experimentally using two independent techniques that allow us to study the dependence of the solar irradiation on the zenith angle and the characteristics of the light extinction in the atmosphere. Our result for the solar luminosity agrees within 7% of the accepted value. This value can be used to estimate the luminosity or power radiated by the Sun. The experiment is inexpensive and conceptually easy to perform and understand.

http://depa.fquim.unam.mx/amyd/archivero/AJP74_0728_1643.pdf

Experimental estimation of the luminosity of the Sun

Efficiency of ceramic absorber coatings for solar-thermal conversion

Typical commercial solar panels consist of approximately 60 individual photovoltaic cells connected in series. Since the usual Kirchhoff rules apply, the current is uniform throughout the circuit, while the electric potential of the individual devices is cumulative. Hence, a solar panel is a good analog of a simple resistive series circuit, except that the devices generate (rather than burn!) electrical power. For example, in order to sustain the current flow, each device must generate the requisite current. As a result, the least efficient device limits the current throughout. Photovoltaic cells also have a more complicated current-voltage (I–V) characteristic, which determines the optimal load for power extraction. These considerations, among others, make the solar panel an excellent platform for exploring the physics of electric circuits.

Circuits in the Sun: Solar Panel Physics

The electromagnetic spectrum emitted by the Sun and reaching the earth comprises of long-waves, radio waves, amateur, microwave, infrared, visible, ultraviolet, x-rays and gamma rays. The contributions of these waves in the evaluation of solar flux, solar constant and total solar irradiance are examined and the possible impacts as well as importance are discussed for the benefit of undergraduate students.

https://dialnet.unirioja.es/descarga/articulo/3694111.pdf

Solar constant versus the electromagnetic spectrum

HE PHYSICS TEACHER ◆ Vol. 42, January 2004 DOI: 10.1 Fig. 1. Schematic representation of the various steps in performing the solar constant experiment. The object of our investigation was to devise an inexpensive, giveaway experiment for measuring the solar constant using equipment inexpensive enough so that we would not be concerned whether or not any of the materials were returned. A search of the literaturel-4 turned up a variety of relatively inexpensive methods, but none of them satisfied our criteria. One method4 used crushed ice and water in a glass container using blackened foil. We tried this method and variations on it but were unable to obtain consistent results. A method using a thermometer to obtain the solar constant from the shape of the temperature vs time plot did yield consistently good results. However, the thermometer violated our financial constraint. The method we settled upon uses energy from the sun, absorbed by aluminum discs, to melt ice, and if the students exercise care they can obtain consistent values for the solar constant. Materials needed are as follows: two plastic foam coffee cups, two 2-in. aluminum discs painted flat black on one side, and one 20-ml disposable plastic syringe. A watch or clock, preferably with a second hand, is to be provided by the student. The student also needs access to a refrigerator in order to freeze two water samples. The procedure is outlined in Fig. 1. Two Styrofoam cups are first prepared as illustrated in A. The two cups are 2/3 filled with water and then frozen (B). The cups then should be allowed to stand for a while outside the freezer to ensure that the ice is at 0°C (C). The top part of each cup is turned upside down and used as a stabilizing base for the bottom half. This becomes important when the sun is not near the zenith. When the ice has reached 0°C, a metal disc is placed on the surface of the ice in each cup, one with the shiny side up and one with the black side up. Any accumulated water

/pdf/the-solar-constant-a-take-home-lab-es446664gr.pdf

Richard DeGeer

Papers

The Solar Constant: A Take Home Lab.

The solar constant: a take home lab [Phys. Teach. 15, 172 (March 1977)]