Explain the experiment to find co efficient of viscosity of liquid using the stocks formula
Answers
Explanation:
Coefficient of viscosity is used to calculate the viscosity of the liquid. Below is an experiment on how to determine the coefficient of viscosity of a given viscous liquid by measuring the terminal velocity of a given spherical body.
Aim
To determine the coefficient of viscosity of a given viscous liquid by measuring terminal velocity of a given spherical body.
Materials Required
A half metre high
5cm broad glass cylindrical jar with millimetre graduations
Transparent viscous liquid
One steel ball
Screw gauge
Stop clock/watch
Thermometer
Clamp with stand
Theory
What is terminal velocity?
Terminal velocity is defined as the highest velocity that is attained by an object as it falls through a fluid. When the sum of drag force and buoyancy are equal to the force of gravity, terminal velocity occurs.
What is terminal velocity formula?
Following is terminal velocity formula:
v=29r2(ρ−σ)η
Where,
v is the terminal velocity
r is the radius of the spherical body
g is the acceleration due to gravity
ρ is the density of the spherical body
σ is the density of the liquid
η is the coefficient of viscosity
Diagram
the coefficient of viscosity of a given viscous liquid by measuring terminal velocity of a given spherical body
Procedure
Clean the glass jar and fill it with transparent viscous liquid.
The vertical scale along the height of the jar must be clearly visible to note the least count.
Check the tight spring of the stopwatch and also record the least count and zero error.
Record the least count and zero error of the screw gauge.
Determine the radius of the ball.
Gently drop the ball in the liquid. Initially, the ball falls with an accelerated velocity until it reaches one-third height of the liquid. Then it falls with uniform terminal velocity.
As the ball reaches some convenient division, start the stopwatch to note its fall.
As the ball reaches the convenient lowest division, stop the stopwatch.
Record the time taken by the ball.
Repeat steps 6 to 9 twice for more readings.
Record the temperature of the liquid.
Record the observations.
Observations
Least count of vertical scale = 1 mm
Least count of stop clock/watch = …….. s
Zero error of stop clock/watch = ……. s
Pitch of screw gauge (p) = 1mm
No.of divisions on the circular scale = 100
Least count of screw gauge (LC) = 1/100 = 0.01 mm
Zero error of screw gauge (e) = …… mm
Zero correction of screw gauge (c) = (-e) = ….. mm
The diameter of the spherical ball
Along one direction, D1 = ….. mm
In the perpendicular direction, D2 = …….. mm
Terminal velocity of spherical ball
Distance fallen, S = …… cm
Time taken,
t1 = …….. s
t2 = …….. s
t3 = …….. s
Calculations
Mean diameter, D=D1+D22mm
Mean radius, r=D2mm=……cm
Meantime, t=t1+t2+t33=…..s
Mean terminal velocity, v=St=….cm.s−1
From formula, η=2r2(ρ−σ)g9v=……C.G.S.units
Result
The coefficient of viscosity of the liquid at a temperature (T℃) = ……. C.G.S.units
Precautions
To watch the motion the liquid used must be transparent
The perfectly spherical ball should be used
Velocity should be noted only when it is constant
Sources Of Error
The density of the liquid used must be non-uniform
The ball used might not be perfectly spherical
Velocity noted might not be constant. HOPE IT HELPS.
