question_answer

Directions : (16-20)

Relation between V, \[\varepsilon \] and r of a cell

Emf of a cell is the maximum potential difference between two electrodes of the cell when no current is drawn from the cell. Internal resistance is the offered by the electrolyte of a cell when the resistance electric current flows through it. The internal resistance of a cell depends upon the following factors; (i) distance between the electrodes (ii) nature and temperature of the electrolyte (iii) nature of electrodes (iv) area of electrodes.

For a freshly prepared cell, the value of internal resistance is generally low and goes on increasing as the cell is put to more and more use. The potential difference between the two electrodes of a cell in a closed circuit is called terminal potential difference and its value is always less than the e.m.f. of the cell in a closed circuit. It can be written as\[V=\varepsilon -Ir\].

The terminal potential difference of two electrodes of a cell is equal to emf of the cell when:

A) \[I\ne 0\]

B) \[I=0\]

C) both [a] and [b]

D) neither [a] nor [b]