Question

In which of the following cells, the potential difference between the terminals of a cell exceeds its emf.

a.

b.

c.

d.

Answer 1

This is a question based on the concept of the emf of the cell. The formula for computing the voltage across the cell, that is, the formula that relates the parameters such as the voltage, the current, the emf and the resistance should be used to solve this problem.

Formula used:
$v=e-ir$

Complete step by step solution:
Firstly, we will define the terms used to solve this question.
Emf – the abbreviation of the emf is electromotive force.
The emf is the electric potential produced by the electrochemical cell.
Potential difference – the difference in the voltage generated at the terminals of a cell.
From the data, we have the data as follows.
The circuit diagrams of the electrical components such as a cell consisting of the emf and voltage should be used.
The formula that relates the parameters such as the voltage, the current, the emf and the resistance is given as follows.
$v=e-ir$
Where v is the voltage, e is the emf, i is the current and r is the resistance.
From the given options the circuit diagram that represents the value of the potential difference between the terminals of a cell exceeds its emf is given as follows.

$\therefore$ In the above circuit, the potential difference between the terminals of a cell exceeds its emf.
As in the circuit diagram (b) the potential difference between the terminals of a cell exceeds its emf.

Thus, the option (b) is correct.

Note:
The direction of the flow of current is the important thing to be known to solve this type of problem. The terms used to define the parameters should also be known. The emf of a cell is different from that of the potential difference across the terminals of the cell, that is, the emf is the internal potential developed, whereas, the potential at the terminals of the cell is the external potential.