If current passing through a potentiometre wire is decreased, then the balancing length will

Explanation

The balancing length in a potentiometer is determined by the point where the potential difference across the wire matches the potential difference of the unknown voltage source. A decrease in current reduces the potential drop per unit length of the wire (potential gradient), meaning that the wire cannot reach the balance point unless it is infinitely long, since the potential difference needed cannot be achieved. Therefore, the balancing length becomes infinite. The other options are incorrect because they do not consider the direct relationship between current and potential gradient in influencing the balancing length.