Electro – motive – Force ( emf ) of a Cell
The energy given by a cell in flowing unit positive charge throughout the circuit completely one time , is equal to the emf of a cell .
Emf of a cell ( E ) = W / q . Its SI unit is volt .
Terminal Potential Difference of a Cell
The energy given by a cell in flowing unit positive charge through till outer circuit one time from one terminal of the cell to the other terminal of the cell .
Terminal potential difference ( V ) = W / q . Its SI unit is volt .
Internal Resistance of a Cell
The obstruction offered by the electrolyte of a cell in the path of electric current is called internal resistance ( r ) of the cell . Internal resistance of a cell
( i ) Increases with increase in concentration of the electrolyte .
( ii ) Increases with increase in distance between the electrodes .
( iii ) Decreases with increase in area of electrodes dipped in electrolyte . Relation between E . V and r
E = V + Ir
r = ( E / V – 1 ) R
If cell is in charging state , then E = V – Ir
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