Dry cell

For the Hard Rock/Heavy Metal band, see Dry Cell (band).

Related Topics:
Hard Rock - Heavy Metal - Band - Dry Cell (band)

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A dry cell is a compact primary electrochemical cell that supplies electrical energy at small currents. Like all electrochemical cells, it gets its electrical energy from an internal chemical reaction. The cell is wrapped in a sheet of zinc, inside which is a carbon rod. The space between the zinc and the carbon is packed with a mixture of moist chemicals. The cell has two contacts: the positive (+) terminal (or cathode) and the negative (-) terminal (or anode).

Related Topics:
Primary - Electrochemical cell - Chemical reaction - Zinc - Carbon - Cathode - Anode

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The anode (-), which is the zinc casing, oxidises according to the following half-equation:

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:Zn(s) → Zn2+(aq) + 2e-

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The graphite rod, immersed in the electrolyte paste (containing manganese dioxide, MnO2), is the cathode (+) and reduces according to the following half-equation:

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:2MnO2(s) + 2H+(aq) + 2e- → Mn2O3(s) + H2O(l)

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Advantages:

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• The dry cell is fairly inexpensive and quite portable due to its compact size
• It can provide small amounts of electricity in remote places.

Disadvantages:

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• This battery can?t be recharged so it has to be discarded, causing pollution
• The anode (Zn) is also the outside layer of the battery, so it can leak, discharging the chemicals inside, when the cell is totally used up. This means that the cell cannot be left in appliances for long periods, as it may leak and ruin the equipment
• Another major problem with this cell is the moist paste inside the battery. This is not completely mobile, so the cell can seem discharged when actually the reaction products have just formed around the anode and cathode, inhibiting further reactions.

Common uses:

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• Torches
• Portable radios and cameras
• All small electrical appliances.