# Electronics/Cells

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## Cells

A cell, or electrochemical cell, Galvanic cell or Voltaic cell, is a component used to store and provide electrical energy. The energy in a cell is stored as a chemical potential energy, and electrical energy can be extracted when the chemicals undergo a chemical reaction. A battery is the term used to refer to multiple cells that are used together as one unit, and can be connected in series, parallel or in a combination of series and parallel connections.
The properties of the cell can be determined by the chemistry of the cell (i.e. what it is made up of), and its physical design. Different chemistries will affect cell voltage, energy density, internal resistivity, and other factors. Physical design will affect the total cell energy capacity, total internal resistance and the shape and size of the cell. Generally, increasing the size of a cell, while maintaining the cell chemistry, will result in a greater energy capacity and lower internal resistance, and consequently a greater current supplying capability, and vice versa.
Cells are categorised as Primary (Dry) cells, and Secondary (Wet) cells, based on their chemistry. Primary cells are single-use and disposable, for example alkaline cells. Secondary cells are rechargeable, for example lead-acid cells.
* Cell: Two materials with a voltage difference between them. This causes current to flow, which does work. Electrons travel from the cathode, do some work, and are absorbed by the anode.
* Anode: Destination of electrons.
* Cathode: Source of electrons.
* ions: An atom with an imbalance of electrons.
* cell operation: The cell runs and electrons are depleted at the cathode and accumulate at the anode. This creates a reverse voltage which stops the flow of electrons.
* irreversible: At some point the voltage difference reactions between the cathode and anode will decrease to a point that the cell in unusable. At this point, in an irreversible cell, the voltage difference is irreplaceably lost, and the cell is of no further use.
* reversible: Able to run the cell backwards.
* rechargeable: In a rechargeable cell, when the voltage difference between the cathode and anode decreases, the cell can be recharged, thereby increasing the voltage difference to a suitable level to allow continued use.
    humid air will discharge cells.
    cells are usually made of toxic or corrosive substances, for example lead and sulphuric acid. Such substances have been known to explode.
* Electronegativity
What is the relationship between voltage and electronegativity?
    Electronegativity is a concept in chemistry used to measure and predict the relative likelihood of a chemical reaction causing electrons to shift from one chemical to another resulting in ions and molecular bonds. A battery cell operates by allowing two chemicals to react and supply ions to the anode and cathode. When the supply of a reactant is consumed, the battery is dead. It no longer produces different electrical potential at the anode and cathode driven by the chemical reaction.
    Voltage is the electrical potential of a point due to surrounding measurable electric charge distributions and points as calculated by application Coulomb's Law. Voltage difference between two points connected by a conductor results in electron flow.