14.1 Cells and Batteries

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

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+
+
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Cell design
• “Cells” are containers of liquid with electrodes:
• 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
Source or use
of electricity
Molten or
aqueous
chemicals
Cell Electrode

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

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

Cell Quantities
Quantity Symbol Meter Units
Charge Q C (coulombs)
Current I ammeter A (ampere)
Potential
difference
V voltmeter V (volt)
Power P W (watt)
Energy
density
J/kg

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

Figure 7 One of the Cells in a 12-V Lead Storage Battery (LSM 14.1C)

Figure 6 A Common Dry Cell Battery (LSM 14.1C)

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

Figure 8 Schematic of the Hydrogen-Oxygen Fuel Cell (LSM 14.1C)

Homework
Textbook p. 614 #1-5
Textbook p. 619 #10-15
LSM 14.1 B,C,D