In a potentiometer experiment, if the area of the cross-section of the wire increases uniformly from one end to the other, draw a graph showing how potential gradient would vary as the length of the wire increases from one end

As Resistance is inversely proportional to the area of cross-section. So, the resistance decreases uniformly as area of cross-section increases uniformly, which implies, V=IR, decreases uniformly.
So, the graph is a straight line with negative slope.