2. Very small pressure differences (PA – PB) can be measured accurately by the two-fluid manometer shown in the figure. Consider the case where p2 – P1 is very small.

Assume that when PA = PB the levels of both liquids are equal to each other. Find an expression for the relationship between PA-PB and h if the reservoir diameter (D) is very large relative to the tube diameter (d). (Note that this would make d/D²negligible.) Explain why this setup makes for a very sensitive manometer,meaning that it can readily measure small pressure differences.