Explanation:
"The accuracy of a potentiometer can be increased by decreasing the potential gradient across the potentiometer wire, and this can be achieved by increasing the length"
The factors that are affecting/limiting the accuracy of the potentiometer are:
The objective of reversing the terminals of the cell
If the jockey of the potentiometer is pressed for a long time, joule heating sets in, so that reversing the terminals of the potentiometer will prevent the resistance due to joule heat from being added to the measured resistance, ultimately preventing unwanted resistance
