Electric Cells and Batteries (Mod.2 pt3 )1 of 2

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How Electric Cells Work

Pie de foto: : In an electric cell, a chemical reaction takes place between the electrodes and the electrolyte solution. This action produces a voltage. The arrows indicate the direction of electron flow.

The cell shown is a container of electrolyte solution with two electrodes suspended in it. The electrolyte is a weak solution of acid, base, or salt in water. The electrodes are two strips of metal; the negative electrode is lead and the positive electrode is lead dioxide. A chemical reaction occurs between the metal electrodes and the electrolyte solution, and as a result, particles in the electrolyte break down into ions. Ions are atoms that have lost or gained electrons. The cell shown is a container of electrolyte solution with two electrodes suspended in it. The electrolyte is a weak solution of acid, base, or salt in water. The electrodes are two strips of metal; the negative electrode is lead and the positive electrode is lead dioxide. A chemical reaction occurs between the metal electrodes and the electrolyte solution, and as a result, particles in the electrolyte break down into ions. Ions are atoms that have lost or gained electrons.

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Wet Storage Cell

Pie de foto: : This figure shows a cutaway view of a wet storage cell.

Construction of a Wet Storage Cell

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Pie de foto: : ln a wet storage cell, each electrode consists of a group of plates or grids.

 This diagram shows the two basic parts of a wet storage cell—the positive electrode and the negative electrode. Each electrode is made up of a group of plates or grids. A group of plates is lined up with spaces between the individual plates. Then, each group of individual plates is welded together and connected by a conducting plate strap. A cell terminal is connected to each plate strap. Both sets of plates are then sandwiched together to form a cell. The two groups of plates are insulated from each other by separators made of insulating material. The positive group of plates (the positive electrode) is connected to the positive cell terminal. The negative group of plates (the negative electrode) is connected to the negative cell terminal.

Dry Cell vs. Wet Cell Batteries

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Pie de foto: : The cell shown in Figure A is a dry cell, like those used in flashlights and transistor radios. The battery shown in Figure B is a wet cell storage battery.

Cells can be classified as either wet cells or dry cells. Wet cells contain a liquid electrolyte (usually dilute sulfuric acid) and produce a little over 2 V. Wet cells are used in forklifts, material handling equipment, and in automobile storage batteries. In contrast, dry cells contain an electrolyte in paste form. In the common flashlight cell, the electrolyte is ammonium chloride paste. A typical dry cell produces about 1.5 V.

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Construction of a Dry Cell

Pie de foto: : Shown here is a cutaway view of a typical dry cell.

 The positive electrode is a carbon rod; the negative electrode is the zinc can. The electrolyte is ammonium chloride, and an absorbent lining surrounds the electrolyte paste inside the can. A steel cover at the top protects the cell. Directly underneath the steel cover is an expansion chamber that allows the electrolyte to expand (under certain conditions) without exploding the battery. A gasket insulates the steel cover from the negative electrode (the zinc can). A washer insulates the steel cover from the positive electrode. The positive and negative electrodes connect to the binding posts of the positive and negative terminals. To protect the zinc can from damage and corrosion, the can is shielded by a cardboard jacket on the outside.

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Pie de foto: : In A, one dry cell has a voltage of 1.5 V. In 8, five cells are connected in series, and the total voltage of the battery is equal to the sum of the individual voltages (7.5 V). Note how the terminals of the cells are linked together in a positive (+) to negative (-) chain.

Connecting Dry Cells in Series

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Connecting Dry Cells in Parallel

Pie de foto: : The cells in this battery are connected in parallel to provide high current. Note that the positive terminals are connected together and the negative terminals are connected together.

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Connecting Dry Cells in Series-Parallel

Pie de foto: : In A, two groups of four cells are connected in series. Then, in B, the cell groups are connected in parallel. A series-parallel arrangement of cells makes it possible for a battery to provide both high current and high voltage to a circuit.