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Instructor Outline:
UM Physics Demo Lab 07/2013
Electrochemical Cells and Batteries
Lab length: 70 minutes
Lab objective: Instruct the students about electrochemical cells, batteries,
electrolytes, anodes, cathodes, voltage, current, resistance and the use of a
multimeter.
Materials
2 plastic beakers
2 metal bars (1 Cu, 1 Zn)
1 U-bar, Cu & Zn
Stack of Cu & Zn disks
paper disks
Cup of Coke (battery acid)
2 plastic spacers
1 Green multimeter
2 banana leads with alligator clips
1 special calculator
1 blue plastic tray (coke containment)
Aluminum foil
Paper towels
Sandpaper
Suggested Demonstrations:
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Dissected Batteries
5E20.10 - Electrolysis of Water
5E40.25 - Lemon Battery
5A50.30 – Van de Graaff Generator & components
Exploration stage: 30 minutes – Group Lab-Work
The students build coke batteries. They observe the role of electrolytes in a
battery, and how series results in a voltage increase. The students then power a
calculator with their coke battery.
Analysis stage: 10 minutes – Lecture
The instructor analyzes the findings in the exploration stage, and answers
questions formed during that stage. Concept development is done on cells, electrolytes,
anodes and cathodes, batteries as connected networks of cells, voltage, current,
conventional current and resistance. The students can use the analysis text to follow
during the lecture, read it at a later time, or use it as a reference only.
Application stage: 20 minutes – Group Lab-Work
The students build batteries with strips of electrolyte soaked paper. They are
challenged to build a 6V battery, but 4.5V is the actual maximum we’ve observed.
Summary: 10 minutes – Lecture
This is a final opportunity for questions to be addressed. This is time to re-iterate
the core concepts and principles.
Concepts developed:
1. Electrochemical cells are very simple devices constructed from an electrolyte
solution, a cathode metal (positive terminal), and an anode metal (negative
terminal).
2. Cells work by electrochemically separating charge and making it energetically
favorable for electrons to flow from higher electrical potential energy to lower
electrical potential energy, that is, from the negative anode to the positive
cathode.
Property of LS&A Physics Department Demonstration Lab
Copyright 2006, The Regents of the University of Michigan, Ann Arbor, Michigan 48109
3. Traveling electrons are a current; the path they take is the resistance of the
external circuit. The electric potential energy available per electron is the
difference in electrical potential or voltage between the anode and cathode.
4. Electrons flow from the negative anode to the positive cathode when a cell
or battery is connected to an external circuit.
5. Conventional current is defined as the flow of positive charges from the
positive cathode terminal of a cell or battery to the negative anode
terminal. This is a commonly used engineering convention and is
completely equivalent to the actual flow of negative electrons from the
negative anode to the positive cathode which actually takes place in any real
circuit.
6. Cells may be connected together to form batteries.
7. Cells connected in series provide a difference in electrical potential which is the
sum of the potential differences for the individual cells. Cells connected in
series provide the same current as a single cell.
8. Cells connected in parallel can provide more current at the same potential
difference as a single cell.
Property of LS&A Physics Department Demonstration Lab
Copyright 2006, The Regents of the University of Michigan, Ann Arbor, Michigan 48109