On what factors does the internal resistance of a cell depend?

Question

Accepted Answer

A cell's internal resistance arises from the resistance the electrolyte and electrode surfaces themselves offer to the flow of ions/charge inside the cell, so it depends on the same kind of factors that govern any conductor's resistance, applied to the cell's own internal geometry and chemistry. It increases with the CONCENTRATION and chemical nature of the electrolyte (different electrolytes, or the same electrolyte at different strengths, conduct ions with different ease); it increases with the DISTANCE between the two electrodes (a longer path for ions to travel means more internal resistance, exactly as a longer wire has more resistance); it decreases with a larger electrode SURFACE AREA in contact with the electrolyte (more area for ions to be exchanged, lowering resistance, just as a thicker wire has less resistance); and it depends o …

Start your 14-day free trial to unlock the full solution →

Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

CBSE 2025Set ANNUAL1 markMCQ
$Q. Which of the following equations gives correct expression for the internal resistance of a cell by using potentiometer?$
(a) r = R(V/E − 1)
(b) r = R(1 − E/V)
(c) r = R(1 − V/E)
(d) r = R(E/V − 1)
›Reveal solutionSolution

Comparing the balancing lengths for a cell on open circuit and on a known resistance box gives the internal resistance of the cell.

In a potentiometer experiment to find the internal resistance $r$ of a cell of emf $E$ : with the key in the resistance-box circuit open, the balancing length $l_1$ gives $E \propto l_1$ . With a known resistance $R$ connected across the cell (so the terminal potential difference is $V$ ), the balancing length $l_2$ gives $V \propto l_2$ . Since $l_1/l_2 = E/V$ , and the current in the circ …

Start your 14-day free trial to see the full solution →
CBSE 2016Set ANNUAL1 markMCQ
$l_1$
›Reveal solutionSolution

In a potentiometer, balancing length is proportional to the potential difference being measured; e.m.f. gives length $l_1$ , terminal p.d. (when shunted by $R$ ) gives length $l_2$ .

In a potentiometer experiment, the balancing length is directly proportional to the potential difference (or e.m.f.) being measured (since the potential gradient along the wire is constant):

$\text{p.d.}\propto l$

When the cell (e.m.f. $\varepsilon$ , internal resistance $r$ ) is balanced directly (open circuit), the balancing length $l_1$ corresponds to its full e.m.f.:

$\varepsilon\propto l_1$

When the cell is shunted by an external resistance $R$ , it drives a current $i=\dfrac{\varepsilon}{R+r}$ through the circuit, and its terminal potential difference becomes …

Start your 14-day free trial to see the full solution →

Q.On what factors does the internal resistance of a cell depend?

Concept understanding — Internal Resistance of a Cell Using Potentiometer

Q.On what factors does the internal resistance of a cell depend?

🎓Unlock everything free for 14 days

Unlock everything free for 14 days