# Determine the Co-efficient of Viscosity by Poiseull’s Capillary Flow method

## Objective:

To determine the co-efficient of viscosity of water by poiseull’s capillary flow method

## Theory:

When a liquid flows through a capillary tube of length l and radius r then the volume of liquid flowing per second is given by, where,

η = Co-efficient of viscosity

P = Pressure difference between two ends = hρg

g = acceleration due to gravity where,

h = difference in height between the two arms of the apparatus = (h2-h1)

ρ = density of liquid

## Apparatus:

Viscosity apparatus, Travelling microscope, cathetometer, measuring cylinder, stopwatch.

## Procedure:

• Measure the length of the capillary tube with the help of a meter scale.
• Measure the radius of the sample capillary tube with the help of the travelling microscope. Determine the Vernier Constant of the microscope. Place the tube on a stand facing the microscope. Focus the orifice. Take reading of the top, down and right ends of the circular orifice.
• Place the water tank of the viscosity apparatus at a certain level. Allow the water to come out of the tube at a very slow rate (drop by drop). Wait until the water levels at two arms of the manometer take steady values.
• Collect water from the output end in a measuring cylinder for a fixed time, say T = 4 minutes. Measure the volume. From that calculate the volume of water collected per second.
• Change the height of the water tank several times and repeat steps 3 and 4.
• Draw a graph with h in abscissa and V in ordinate. The curve should be a straight line passing through the orifice. If there is a curvature for high values of h, use the linear portion to calculate the slope.

## Experimental Results:

Vernier constant of the travelling microscope:

Measurement of radius of Capillary tube:  ## Calculation:

Percentage error: ## Conclusion:

error: Content is protected !!