In a potentiometer, the null point is receive | vedclass

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(B) The potential difference across a length $l$ of the potentiometer wire is given by $V = kl$, where $k$ is the potential gradient. The null point i

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Increase resistance in the main circuit

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(B) The potential difference across a length $l$ of the potentiometer wire is given by $V = kl$, where $k$ is the potential gradient. The null point is obtained when the $EMF$ of the cell, $E$, equals the potential drop across the wire length $l$, so $E = kl$. To shift the null point to a higher length (from $7^{th}$ wire to $9^{th}$ wire), we need to decrease the potential gradient $k$. Since $k = \frac{V}{L} = \frac{IR}{L}$, where $I$ is the current in the potentiometer wire, $R$ is the resistance of the wire, and $L$ is the total length, decreasing $k$ requires decreasing the current $I$. This is achieved by increasing the resistance in series with the potentiometer wire in the main circuit.

In a potentiometer, the null point is received at the $7^{th}$ wire. If we now want to shift the null point to the $9^{th}$ wire, what should we do?

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