Let this minimum corresponds to a line of intersection AB. By rotating the plane around the normal the radius of curvature will go through a minimum. Note that this radius is not yet the principal radius. The radius of curvature for this line (which in general will be curved) is that for a circle tangent to the line at point O. A plane which contains the normal will eventually intersect the surface to a line of intersection (is not shown). Let O is a point and Z is the normal to the surface at that point. Hence we calculate the radius of the bore (r).Mean curvature. The inner diameter of the capillary tube is measured using the travelling microscope. The difference between the two readings gives the height of the water column inside capillary (h). The microscope is lowered and it is focused on the water level inside the beaker. The reading is taken using the microscope. Using a travelling microscope, the microscope is focused on the lower meniscus of the curved concave surface. The phenomenon is known as capillary action or
This relation is known as Jurin’s Law.Ĭapillary tube is dipped in a beaker containing liquid (say water) whose
inversely proportional to the density of the liquid.inversely proportional to the radius of the bore of the capillary tube.To which the liquid rises in the capillary tube is This is an expression for the rise in the liquid Where ‘V’ is the volume of liquid in capillary and ρ is theĭensity of the liquid in the capillary tube. Where ‘m’ is the mass of liquid in the capillary tube. Total upward force = Weight of liquid in the capillary The liquid goes on rising till the force of surface tension isīalanced by the weight of the liquid column. The weight of liquid acts verticallyĭownward. Hence total upward force is 2πr Tįorce the liquid rise up in the tube. The radius of the bore of the capillary tube, the length along which the force Rise in the liquid layer in the capillary tube. Will push the liquid up into the capillary tube. Radially outward (opposite to each other). The components Tsinθ cancel each other as they are equal in magnitude and Is resolved into two components vertical Tcos θ and horizontal T sin θ. Tension ‘T’ acts along the tangent to the liquid surface at the point ofĬontact as shown. Due to depression in the level of mercury in a capillary tube, a correction is to be applied for mercury barometer.
Thus the loss of water in the soil is prevented. The loosening of the top layer of the soil breaks up the fine capillaries through which the deeper down water is sucked up. To conserve soil water, the farmers plough their fields in summer. Soil water rises to the surface by capillary action and evaporates.To avoid it, the base is made using damp-proof cement. Bricks and mortar, which are porous, permit the rise of soil water through them by capillary action.Due to capillary action liquids are absorbed by sponges.Due to capillary action ink is absorbed by blotting paper.Due to capillary action water rises through the sap of trees.Due to capillary action oil rises through wicks of lamps.When chalk piece is dropped in water, due to capillary action water enters the pores of the chalk. Due to which the trapped air comes out of the pores in the form of bubbles. When chalk piece is immersed in water, bubbles are emitted:Ĭhalk is porous in nature. Examples of capillarity: Blotting paper absorbs ink or water, ink rises in a pen, oil rises in wicks of a lamp.
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