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JAMB Physics 2024 Paper

Question : 56

Total: 125

Solution:

Concept:

In a potentiometer, the balance length is directly proportional to the e.m.f of the cell being measured.

Explanation:

Let the first e.m.f be

E_1 = 3.06\,V

and its balance length be

L_1 = 75\,cm

Let the second e.m.f be

E_2 = 2.295\,V

Since

L \propto E

, we can write:

\frac{L_1}{L_2} = \frac{E_1}{E_2}

Rearrange to find

L_2

L_2 = L_1 \times \frac{E_2}{E_1}

Substitute the given values:

L_2 = 75 \times \frac{2.295}{3.06}

L_2 = 75 \times 0.75 = 56.25\,cm

This is approximately

56.26\,cm

Answer:

The new balance length is

56.26\,cm

, which is option A.

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