Meritve lastnosti galvanskih členov : diplomsko delo

Šček, Urban (author), Bajc, Jure (mentor)

V nalogi se osredtočamo na to, kako pri pouku izvajati meritve lastnosti galvanskih členov. Ena izmed lastnosti galvanskih členov je notranji upor. Ravno tej lastnosti, se v nalogi še posebej posvetimo. Za merjenje notranjega upora poznamo več različnih metod. Ena izmed njih je merjenje preko bremena, pri kateri merimo napetost na bremenu ter tok po vezju. Iz izpeljane enačbe vezja nato sledi izračun notranjega upora. Sam pa sem notranji upor določeval po metodi, ki vkjučuje neposredno merjenje napetosti na galvanskem členu. Od vira želimo, da ima čim manjši notranji upor in čim večjo gonilno napetost. Z izvedbo eksperimenta pokažemo, da je notranji upor galvanskega člena tisti, ki se spreminja, in ne gonilna napetost, ki je konstantna, in značilna za izbrano kombinacijo elektrod in elektrolita. Med drugim želimo pokazati, da je pomembna pravilna interpretacija meritev. V povezavi s tem pokažemo, da je naivna ideja, da lahko z voltmetrom direktno izmerimo gonilno napetost, le pogojno veljavna. Veljavna je le v primeru idealnega voltmetra, to je voltmetra z neskončnim uporom oziroma z uporom, ki je za več velikostnih redov večji od notranjega upora člena. V nadaljevanju naloge izmerimo nekaj tipičnih karakteristik preprostih galvanskih členov in jih kvalitativno pojasnimo. Poleg tega, za nekaj različnih geometrij preverimo, kako dobro različni preprosti modeli opišejo odvisnost notranjega upora člena, od vrednosti značilnih parametrov galvanskega člena. Pogosto odvisnosti dobro opišemo s preprostim modelom člena kot električnega vodnika, model le malenkost posplošimo.

• Language: Slovenian
• Keywords: galvanski člen, notranji upor, merjenje toka, napetosti in upora, redoks reakcije
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: PEF - Faculty of Education
• Publisher: [U. Šček]
• Year: 2017
• Number of pages: 32 str.
• PID: 20.500.12556/RUL-96344
• UDC: 544.643:621.352.1(043.2)
• COBISS.SI-ID: 11739465
• Publication date in RUL: 02.10.2017

Secondary language

• Language: English
• Title: Measurements of galvanic cell properties

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.

• Keywords: physics, fizika