eolas/Electronics/Cells_and_batteries.md

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Electronics	physics electricity

Cells and batteries

Cells are a voltage source that generate a difference of potential via a positive and negative electrode separated by an electrolytic solution. The electrolytes pull free electrons from one of the materials which creates a positive charge. The other material gains the free electrons creating a negative charge.

A battery is a combination of two or more cells.

Cells which cannot be recharged are called primary cells. Cells which can be recharged are called secondary cells.

Connecting batteries

Cells and batteries can be connected to each other in electrical ciruits to increase the overall voltage that is produced. There are three main connection types:

• series
• parallel
• series-parallel

Series connections

With series connections we distinguish series aiding and series opposing configurations.

In the case of series aiding, cells are connected one in front of another with the positive terminal connecting to the negative terminal of the other in a line.

In this configuration the same current flows through all the cells. This is represented mathematically as follows (T stands for time):

I_{T} = I_{1} + I_{2} + I_{3} \

The voltage is the sum of the individual cell voltages (represented here as electrical field).

E_{T} = E_{1} + E_{2} + E_{3} \

Note here we use E instead of V. Strictly, V denotes the potential difference whereas E denotes the electric field. The electric field is the physical field that surrounds each electric charge and exerts force on all other charges in the field, attracting or repelling them

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