Question:

A cell, shunted by a 8 Ω resistance, is balanced across a potentiometer wire of length 3 m. The balancing length is 2 m when the cell is shunted by 4 Ω resistance. The value of internal resistance of the cell will be _____ Ω.

Updated On: Mar 19, 2025
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Correct Answer: 8

Solution and Explanation

A cell, shunted by a 8 Ω resistance, is balanced across a potentiometer wire of length 3 m
\(\frac {ε_18}{r_1+8}3c\)
\(\frac {ε_14}{r_1+4}2c\)
\(⇒ \frac {2(r_1+4)}{r_1+8}=\frac 32\)
Then, the value of internal resistance of the cell,
\(⇒ r_1 = 8 Ω\)
So, the answer is \(8 Ω\).
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Concepts Used:

Electric Current

Defining Electric Current

It is the rate of flow of electrons in a conductor. SI Unit - Ampere (A).

Electrons are negatively charged particles hence when they move a number of charges moves.

Note:- The ability of a particular substance to conduct electricity depends on the number of electrons that are able to move . Some of the materials allow current to flow better than others. 

What is an Electromotive Force?

If a force acts on electrons to make them move in a particular direction, then up to some extent random motion of the electrons will be eliminated. An overall movement in one direction. The force which acts on the electrons to move them in a certain direction is known as electromotive force and its quantity is known as voltage and is measured in V.