CELLS, EMF, INTERNAL RESISTANCE

By Kunal Kapoor

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


The electrolytic solution is the one which provides reaction components to anode and cathode. It reacts with the metals in cathode and anode to create charges, which then flow through the two nodes.



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 




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