# CELLS, EMF, INTERNAL RESISTANCE

A Cell is
a simple device to maintain a steady current in an electric circuit . It
consitits of following components

- Electrodes
- Cathode

A cathode is the positive electrode in a cell

- Anode

An Anode is the negative electrode in a cell

- Electrolytic solution

As given in diagram
above, a cell has two electrodes, called the positive (P) and the
negative (N),

They are
immersed in an electrolytic solution. Dipped in the solution, the electrodes
exchange charges with the electrolyte

The cathode or positive terminal develops V+ potential and anode or negative terminal gets V- potential

The Potential developed across two nodes is . This value always is greater than zero.

In above case when R is a finite value and I is a non zero value

thus

where r is the internal resistance of cell.

In practical cases, r is neglected as

Thus as pers Ohms law across Resistance R is V = IR

Combining equations gives us