Contributed by:
The highlights are:
1. Origin of the cells
2. Cell design
3. Voltaic cells
4. Properties of cells
5. Cell quantities
6. Secondary cells and batteries
7. Fuel cells
1.
14.1 Cells and Batteries
2.
Origins of the Cell
• Galvani (late 1700’s) observed a frog’s leg
twitch when exposed to a current
• Volta (early 1800’s) realized it was due to
current flowing through electrolytes in body
• Volta invented the first battery by
connecting multiple electric cells together
• Based on spontaneous redox rxtn’s it was
able to produce a consistent current
3.
Cell design
• “Cells” are containers of liquid with electrodes:
Source or use
of electricity
Cell Electrode
–
–
+
+
Molten or
– + aqueous
chemicals
• In “voltaic cells”, electricity is produced
spontaneously from a redox reaction
• In “electrolytic cells”, electricity is used to force
chemicals to undergo a redox reaction
4.
Voltaic Cell
• also referred to as a “galvanic cell”
• salt bridge or porous disk(cup) used to allow for
unrelated ions to move to allow for balance of charge
5.
Cell Properties
- driving force on electron to move them through the
wire
• electric potential difference is the energy difference
per unit charge
• depends on type of electrodes and electrolytes used in
cells
• electric current is rate of flow of charge in a circuit
• power is the rate at which electrical energy is
produced
6.
Cell Quantities
Quantity Symbol Meter Units
Charge Q C (coulombs)
Current I ammeter A (ampere)
Potential V voltmeter V (volt)
Power P W (watt)
Energy J/kg
7.
Secondary Cells & Batteries
a battery is a group of galvanic cells
connected in series
the potentials of the individual cells add
to give the total battery potential
secondary cells can be recharged by
adding electricity
8.
Figure 7 One of the Cells in a 12-V Lead Storage Battery (LSM 14.1C)
9.
Figure 6 A Common Dry Cell Battery (LSM 14.1C)
10.
Fuel Cells
... voltaic cells where the reactants are
continuously supplied.
2H2(g) + O2(g) 2H2O(l)
anode: 2H2 + 4OH 4H2O + 4e
cathode: 4e + O2 + 2H2O 4OH
11.
Figure 8 Schematic of the Hydrogen-Oxygen Fuel Cell (LSM 14.1C)
12.
Homework
Textbook p. 614 #1-5
Textbook p. 619 #10-15
LSM 14.1 B,C,D
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