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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