Question

The difference in pressure head, measured by a mercury water differential manometer for a 20 cm difference of mercury head will be

• A. 2.72 m
• B. 2.52 m
• C. 2.0 m
• D. 0.2 m

Answer 1

The correct option is B 2.52 m

$Differenceinpressurehead=20cm\times (13.6-1)=252cm=2.52m.$

$Proof:$


$Pressureatsectionx-x;$

$P_A+{\rho }_{2}g(x+h)=P_B+{\rho }_{2}gx+{\rho }_{1}gh$

$P_A-P_B={\rho }_{1}gh-{\rho }_{2}gh$

${\rho }_{2}g{h}^{\prime }={\rho }_{1}gh-{\rho }_{2}gh$

$h^{\prime }=(\frac{{\rho }_1}{{\rho }_2}-1)h$