TGPSC HMWSSB Manager 2015 Paper 2 · Question 32

Question 32 of the TSPSC Manager (Engineering), HMWSSB, 2015: Paper 2 (Civil Engineering) (1 November 2015). Try it first, then open the answer and explanation.

1. Manager 2015 Paper 2 (Civil) · Q32 · Geotechnical Engineering · Soil Mechanics

   If R_1 and R_2 are the radii of curvature of a non-uniform meniscus in two orthogonal planes, the capillary rise is given by:

   1. h_c = (σ/γ_w){R_1 + R_2}
   2. h_c = (σ/γ_w){(1/R_1) + (1/R_2)}
   3. h_c = (σ/γ_w){R_1 × R_2}
   4. h_c = (σ/γ_w){R_1/R_2}
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   Answer: (2) h_c = (σ/γ_w){(1/R_1) + (1/R_2)}

   By Laplace's equation, the pressure difference across a curved meniscus is σ(1/R_1 + 1/R_2); equating it to the weight of the raised column, γ_w h_c, gives h_c = (σ/γ_w)(1/R_1 + 1/R_2). For a spherical meniscus (R_1 = R_2 = R) this reduces to the familiar 2σ/(γ_w R).

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