Measurements of galvanic cell properties

Urban Šček (2017) Measurements of galvanic cell properties. Diploma thesis.

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Abstract

My diploma thesis deals with how to perform measurements of galvanic cell properties in the classroom. One of the galvanic cell properties is the internal resistance. We pay a lot of attention especially to this property. There are many different methods for measuring internal resistance. One of them is using the circuit with a known resistor. The voltage across the resistor and the electric current through the circuit are measured. From several measurements with different resistors the internal resistance is relatively easy to determine. I decided to choose a method, which comprises direct voltage measurement across the galvanic cell. It is desired for an electric source to have as small as possible and as big electromotiv force (terminal voltage when no current is flowing) as possible. We show experimentaly, that the internal resistance of the galvanic cell is changing and not the electromotive force of the source, which is constant and typical for the chosen combination of the electrodes and the electrolyte. I also wanted to show, that the correct interpretation of the measurements is important. In relation to this we show that the idea of the direct measurement of the electromotive force of a source with voltmeter is a naive idea. It is correct only in the case of using an ideal voltmeter. That is a voltmeter with infinite resistance or with a resistance that is much bigger than the internal resistance of the cell. Furthermore, we measure some typical characteristics of simple galvanic cells and we explain them qualitatively. Additionally for some different geometries we check, how well simple models describe dependence between the internal resistance of the cell and the values of typical parameters of the galvanic cell. Very often we can describe these dependences with a model of a wire, made of a conducting material, which needs to be generalised a little.

Item Type: Thesis (Diploma thesis)
Keywords: galvanic cell, internal resistance, measurements of electric current, voltage and resistance, redox reactions
Number of Pages: 32
Language of Content: Slovenian
Mentor / Comentors:
Mentor / ComentorsIDFunction
doc. dr. Jure BajcMentor
Institution: University of Ljubljana
Department: Faculty of Education
Item ID: 4770
Date Deposited: 28 Sep 2017 08:56