Question

Rise of water in a glass capillary tube will be mininmum at
A) equator
B) poles
C) height of 100km above the surface of earth
D) same at all places

Answer 1

Answer:

B) POLES

Explanation:

Formula for rise of liquid in capillary =>  h = (2Scosθ)/rρg

so,

h ∝ 1/g

so rise of liquid will be minimum where g is maximum.

We know, value of g increases as we move from equator to poles.

since g is max at poles so rise will be minimum.

Hope this helps!

Answer 2

The rise of water in a glass capillary tube will be minimum at B) poles.

• If a liquid with density d and surface tension T makes an angle of contact ∅ and rises to a height h in a capillary tube of radius r then the height h is given by the formula:

        h = 2 T cos∅ / rdg

• Hence the height h is inversely proportional to acceleration due to gravity g.

• The value of g varies with the latitude of the Earth as:

        g' = g - Rω² cos²θ

• Here R is the radius of the Earth, ω is the angular velocity and θ is the latitude angle.
• At poles, θ = 90° so g’ = g.
• At the equator, θ = 0° so g′= g – Rω².
• Since g at poles is greater than at the equator, the rise in the capillary is smaller at poles.