Physics Coursework Analysing Data - page 1
Keywords: Physics Report Analysising Data Extracting Information Calculation Potato Batteries
By Jenny on 02/07/2009
Level: A Level (Year 13)
Page Number: 1 of 5 pages: 1 2 3 4 5
Physics Coursework – Potato Project
For this coursework I am analysing data. We did an initial experiment to measure the current, potential difference and external resistance of a “potato battery”. Now I will extract as much information as possible from these values by analysing them, drawing graphs and making calculations.
Circuit Diagram for experiment
How the experiment works - Standard Electrode Potentials
An electrochemical cell which causes external electric current flow can be created using any two different metals since metals differ in their tendency to lose electrons. Zinc more readily loses electrons than copper, so placing zinc and copper metal in solutions of their salts can cause electrons to flow through an external wire which leads from the zinc to the copper. In our potato the electrons flow through the salts in the potato.
The electrochemical cell is created by placing the metallic electrodes into the electrolyte (the salts in the potato) where a chemical reaction either uses or generates an electric current. Electrochemical cells which generate an electric current are called voltaic cells or galvanic cells, and common batteries consist of one or more such cells. Our potato is one of these.
The electric potential is created between the two dissimilar metals. This potential is a measure of the energy per unit charge which is available from the oxidation/reduction reactions to drive the reaction. You can think of the cell reaction in terms of two half-reactions, an oxidation half-reaction and a reduction half-reaction.
Cu2+ (aq) + 2e- → Cu (s)
Zn (s) → Zn2+ (aq) + 2e-
The cell potential (often called the electromotive force or emf) has a contribution from the anode which is a measure of its ability to lose electrons - its "oxidation potential". The cathode has a contribution based on its ability to gain electrons, its "reduction potential". The cell potential can be written:
Ecell = oxidation potential + reduction potential
The maximum voltage which can be produced between the poles of the cell is determined by the standard electrode potentials under standard conditions.
In our cell zinc and copper were used as electrodes. The data from the table of standard electrode potentials is
Cathode (Reduction)
Half-Reaction Standard Potential
E° (volts)
Zn2+(aq) + 2e- -> Zn(s) -0.76
Cu2+(aq) + 2e- -> Cu(s) 0.34
Since the standard electrode potentials in the table are reduction potentials, the one which is most negative will need to be reversed in sign to get its oxidation potential.
The cell potential is
Ecell = oxidation potential + reduction potential
Ecell =
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