The factors that affect the VOLTAGE RATING of a cell are the material the electrodes are made
of and the composition of the electrolyte.
The voltage rating of a cell that has a dilute solution of ammonium chloride (sal ammoniac) for
its electrolyte, and electrodes made of carbon and zinc, is 1.5 volts.
The factors that affect the CURRENT CAPACITY of a cell are the size of the electrodes, the
distance between them in a solution of electrolyte, and the temperature.
The current capacity of a cell is expressed in AMPERE-HOURS. Ampere-hours of a cell is the
measurement of current capacity that indicates the amount of current that will flow through a
circuit in a certain amount of time.
The ampere-hours, or current capacity of a cell is affected by the size of the electrodes,
distance between the electrodes in the electrolyte, and the temperature.
When current flows through a cell, it causes gas bubbles to form and some of them
accumulate on the positive electrode. The accumulation of gas bubbles tends to reverse the
polarity of the cell, thus increasing the effective resistance of the cell. This reduces the
current flow and lowers the voltage available at the cell terminals.
The result of the chemical reaction that causes the accumulation of gas bubbles on the
positive electrode of a cell is POLARIZATION.
The impurities in the materials used to make electrodes and electrolyte cause a chemical
action to take place in a cell when the circuit is open. This chemical action will discharge a
cell when it is not supplying power to a circuit.
The chemical action, of an open-circuit cell, that takes place because of the impurities in the
materials used to make electrodes an electrolyte causes LOCAL ACTION which will discharge
the cell.
When a lead-acid cell is being discharged, a chemical reaction takes place that causes the
sulfuric acid in the electrolyte to combine with the lead plates, which forms lead sulfate.
The formation of lead sulfate coats the electrodes with lead sulfate and decreases the acid
content of the electrolyte. The result of this chemical reaction is LEAD SULFATION.
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