Today, galvanic cells are among the most common chemical current sources.Despite their shortcomings, they are widely used in electrical and constantly improved.
Operating principle
The simplest example of the operation of the cell looks like.In a glass jar with an aqueous solution of sulfuric acid was immersed two plates: one - copper, the second - zinc.They are the positive and negative poles of the cell.If these poles to connect the conductor to obtain a simple electrical circuit.Inside the current will flow from the zinc plate having a negative charge to the copper positively charged.In the outer chain motion of charged particles in the reverse direction.
Under the influence of a current of hydrogen ions and the acid residue of sulfuric acid will move in different directions.Hydrogen will give his charges a copper plate, and acid residue - zinc.So at the terminals of the element voltage is maintained.At the same time on the surface of the copper plate will settle hydrogen bubbles, which will weaken the effect of the cell.Hydrogen creates together with the metal plate further voltage which electromotive force is called polarization.The direction of this charge is opposite to the charge emf emf cell.Bubbles themselves create additional resistance element.
we reviewed item - a classic example.In reality, these cells have simply not used because of the high polarization.That it did not occur in the manufacture of elements in their formulation is a special substance that absorbs the hydrogen atoms, which is called the depolarizer.Typically, this drugs containing oxygen or chlorine.
advantages and disadvantages of modern electrochemical cells
Modern galvanic cells are made of different materials.The most common and familiar type - a zinc-carbon elements used in the penlight batteries.These advantages include relatively low cost, to the downside - a small shelf life and low power.
more comfortable option - it is alkaline cell.They are also called zinc-manganese.There is no electrolyte type dry matter coal, and an alkaline solution.Discharged, such elements do not emit virtually gas, so they can be made airtight.The shelf life of such elements is higher than the zinc-carbon.
Mercury elements similar in structure to alkaline.There used mercuric oxide.Such power sources are used, for example, for medical equipment.Their advantages - resistance to high temperatures (up to 50, and in some models up to 70? C), voltage stability, high mechanical strength.Disadvantage - the toxic properties of mercury, because of which the exhaust-life elements must be handled very carefully and sent for recycling.
Some elements are used for the manufacture of silver oxide cathodes, but because of the high cost of metal using them uneconomical.More common elements with lithium anodes.They are also quite expensive, but have the greatest power of all the above types of electrochemical cells.
Another type of battery cells - a concentration cell.In their process of particle motion may proceed with the transfer and no transfer of ions.The first type - is an element in which two similar electrodes immersed in electrolyte solutions of different concentration separated by a semipermeable membrane.In such elements EMF is due to the fact that the ions are transferred into a solution with a lower concentration.The elements of the second type electrodes made of different metals, and the concentration leveled by chemical processes that take place at each of the electrodes.The electromotive force of these elements is higher than the elements of the first type.
