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Water rises in a vertical capillary tube upto a beight of 2.0 cm. If tube is inclined at an angle of $ 60^ \circ $ with the verticalthen the what length the water will rise in the tube.
$l = { h \over cos \theta } = { \alpha \over cos 60 } = 4.0 cm $
The lower end of a glass capillary tube is dipped in water rises to a height of 8 cm the tube is then broken at a height of 6 cm. The height of water column and engled as contact will be
When a capillary tube is broken at a height of 6 cm the height of water column will be 6 cm. $ As h = { 25 cos \theta \over \rho rg } or { h \over cos \theta } = constant $ $ { 8 \over cos 0 ^\circ } = { 6 \over cos \theta } or cos \theta = { 6 cos \theta \over 8 } = {3 \over 4} $ $ \therefore \theta = cos ^ {-1} \left( {3 \over 4} \right) $
A large number of water drops each of rdius r combine to have a drop of radius R. If the surface tension is T and the mechanical equivalent at heat is J then the rise in tempreature will be
Rise in tempreture $ \triangle \theta = { 3T \over Jsd } \left( {1 \over r } - { 1 \over R} \right) $ $ \triangle \theta = { 3T \over J} \left( {1 \over r } - { 1 \over R} \right) $ (For water S = 1 and d = 1)
When liquid medicine of desting S is to be put in the eye. It is done with the help of a dropper as the bulb on the top of the dropper is pressed a drop forms at the opening od the dropper we wish to estimate the size of the drop. We dirst assume that the drop formed at the opening is spherical because the requires a minimum increase in its surface energy. To determine the size we calculate the net vertical force due to surface tension T when the radius od the drop is R. When this force becomes smaller than the weight of the drop the drop gets detched from the dropper. If the radius od the opening od the dropper is r ; the vertical force due to the surface tension onthe drop of radius R. (assuming r << R) is
Due to surface tension vertical force on drop $ Fv = T_2 \pi r Sm \theta $ $ = T_2 \pi r { r \over R} = T {2 \pi r^2 \over R } $
When liquid medicine of desting S is to be put in the eye. It is done with the help of a dropper as the bulb on the top of the dropper is pressed a drop forms at the opening od the dropper we wish to estimate the size of the drop. We dirst assume that the drop formed at the opening is spherical because the requires a minimum increase in its surface energy. To determine the size we calculate the net vertical force due to surface tension T when the radius od the drop is R. When this force becomes smaller than the weight of the drop the drop gets detched from the dropper. .$ If l = 5 \times 10^ {-4} m, \rho = 10^ 3 kg m^{-3} = 10 ms ^ {-2 } T = 0.11 N m^{-1} $ the radius of the drop when it detaches from the dropper is approximately
$ { 2 \pi r^2 \over R } T = \rho { 4 \over 3} \pi R^3 .9 $
When liquid medicine of desting S is to be put in the eye. It is done with the help of a dropper as the bulb on the top of the dropper is pressed a drop forms at the opening od the dropper we wish to estimate the size of the drop. We dirst assume that the drop formed at the opening is spherical because the requires a minimum increase in its surface energy. To determine the size we calculate the net vertical force due to surface tension T when the radius od the drop is R. When this force becomes smaller than the weight of the drop the drop gets detched from the dropper. After the drop detaches its surface energy is
$ U = T - A = 0.11 \times 4 \pi ( 1.4 \times 10 ^ {-3} )^2 $
Assertion & Reason type questions Read the assertion and reason carefully and mark the correct option given below. Assertion : When height of a tube is less then liquid rise in the capillary tube the liquid does not overtow. Reason : Product of radius of meniscus and height of liquid incapilling tube always remains constant.
$ h = { 2T \over Rdg } \Rightarrow hR= { 2T \over dg } $ $ \therefore hR =constant $ Hence whenthe tube is of insufficient length radius of curvature of the liquid meniscus increassesso as to maintain the product hR a finite constant. i.e. as h decreases R increases and the liquid meniscus becomes more and more flat but the liquid does not overflow.
Assertion & Reason type questions Read the assertion and reason carefully and mark the correct option given below. Assertion : The concept of surface tension is help only for liquids. Reason : Surface tension does not hold for gases.
We know that the intermolecular distance between the gas moleculas is Large as compaired to that of liquid Due to it the forces of cohesion in the gas moleculas are very small and these are quite Large for liquids. Therefor the concept of surface tension is applicable to Liquid but not to gasses
Assertion & Reason type questions Read the assertion and reason carefully and mark the correct option given below. Assertion : The water rises higher in a capillary tube of small diametre than in the capillary tube of large diamtre. Reason : Height through which liquid rises in a capillary tube is inversely proportional to the diameter of the capillary tube.
The height ofcapillary rise is inverslypropostional to radius (or diametre) of capillary tube i.e. $ h \alpha { 1 \over r } $ so, for smaller r the value of his higher
Assertion & Reason type questions Read the assertion and reason carefully and mark the correct option given below. Assertion : Tiny drops of liquid resist deforming forces better than bigger drops. Reason : Excess pressure inside a drop is directly proportional to surface tension.
When a drop of Liquid is poured on a glass, plate, the shape of the drop also is governed the force of gravity for every small drops the potential energy due to gravity is insignification. Compared to that due to surface tention. Hence, in this case the shape ofthe drop is determined bysufrace tension alone and drope becomes spherical.
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