Investigatory Project on Solenoid
Investigatory Project on Solenoid and the Magnet
Aim: To study the variation of force of attraction between a solenoid and a bar magnet with the current flowing through the solenoid.
Materials and apparatus required: A short solenoid of thin insulated copper wire having a large number of turns wound over a pvc pipe of radius about 0.5 cm and length about 3 cm, a bar magnet, a 4volt battery, a rheostat, an ammeter, a accumulator, common balance, etc.
Principle:
A current carrying solenoid acts like a bar magnet. The strength of the magnetic field along its axis due to the current through a solenoid depends on (1) the current i flowing through the solenoid and (2) the number of turns per unit length n of the solenoid. As a result of it, the force of interaction between a bar magnet and the current carrying solenoid can be changed by (1) varying current and (2) varying the distance between them.
Experimental set up:
The bar magnet is suspended vertically from the stirrup at one of the ends of the beam of the common balance after removing the pan from there. The other pan is left as it is and weight are added in this pan to counter balance the weight of the magnet. The solenoid is placed just below the magnet such that the axis of the solenoid coincide with the axis of the bar magnet. The distance between the lower end of the magnet and the upper end of the solenoid should be kept constant.
The solenoid is connected in series with the battery, rheostat and ammeter through a commutator.
Procedure
The commutator is put in one direction and the rheostat is adjusted to send a suitable current. If there is a repulsion between the solenoid and the magnet, reverse the direction of current through the solenoid using the commutator to make the force attractive. Weights are added in the pan to balance the attractive force between the solenoid and the bar magnet. The additional weight m added in the pan is noted. Repeat the experiment for different values of current.
A graph is drawn taking the force of attraction, F = mg, along the yaxis and the current along the xaxis. The graph is a straight line.
Observations
Trial 
Ammeter reading i(A) 
Weight added in the pan m(kg) 
Force of attraction, F = mg(N) 
1 



2 



3 



4 



…. 



Conclusion
The straight line graph shows that the force (F) of attraction between the current carrying solenoid and the bar magnet is directly proportional to the current (i) passing through the solenoid.
Fluid Mechanics Viva Questions
Fluid Mechanics Lab Viva Questions and Answers
1. What is the unit of Viscosity and kinematic viscosity?
The unit of viscosity is Poise
The unit of kinematic viscosity is Stock
2. With respect to water column, the measured atmospheric pressure is?
10.3 m
3. How will thou calculate the gauge pressure of a particular point?
The gauge pressure is the difference of absolute pressure and atmospheric pressure.
Gauge pressure = Absolute pressure 
Atmospheric pressure
4. How the velocity at a point is measured?
By using a Pilot tube
5. How can you measure the flow rate (discharge) through a pipe?
By a Venturimeter
6. In terms of C_{v} and C_{c}, how the coefficient of discharge calculated?
Coefficient of discharge = C_{v} x C_{c}
7. What is the use of a current meter?
The main application of the current
meter is for measuring the velocity.
Current meter can be used in waterways, channels, rivers and the sea to
precisely calculate the current velocity. It is also possible to apply the
metre to contaminated water currents.
8. How can you measure the velocity from a current meter?
With the propeller mounted on the rods
attached to a wire, the velocity from a current meter is measured.
9. In a rectangular channel, when the discharge is maximum?
The discharge is maximum through a
rectangular channel, when
m = d/2
Where' m' and 'd' are the hydraulic mean
depth and the depth of flow
10. Write down the chezy's formula?
The chezy's formula is
Q = AC√(mi)
Where,
A = the
area of flow of water,
m
= the hydraulic mean depth (hydraulic radius),
i = slope of the bed and
'C'
= Chezy's Constant.
The velocity can be calculated as:
V = C√(mi)
11. In a trapezoidal channel, when the
discharge is maximum?
The discharge is maximum when, half of top width equals the sloping side.
i.e., Half of top width = Sloping side
12. How will you define the critical
depth?
When the specific energy is minimum, the depth of flow can be named as the 'critical depth'.
NOTE:
• When the flow depth is 0.81 diameter, the maximum discharge through a circular channel is obtained.
• In a v notch, the rate of flow varies as H5/2.
• The kinetic energy per unit weight is V2/2g.
• From higher energy to lower energy, the liquid flow takes place.
• In a venturimeter, the outlet length is greater than the inlet length.
• The sum of pressure head, kinetic head and datum head gives the Total Energy Line (TEL).
• It is necessary that the liquids using in manometers should have high surface tension.
• We know that Kaplan turbine is a propeller turbine in which it is possible to change the vanes fixed to the hub.
• The specific gravity of water is equal to 1, and the specific gravity has no unit.
• The coefficient of velocity has an average value of 0.97.
• The discharge in an open channel is maximum corresponds to its critical depth.
• The application of a pilottube is for measuring the velocity at a point.
13. How will you define the Reynolds number?
The Reynolds number can be defined as
the ratio of inertial force to the viscous force.
Reynolds number = Inertial force/Viscous force
14. What is the use of a notch?
The main use of a notch is to measure
the rate of flow through a small channel.
15. What is the coefficient of
contraction?
The ratio between the area of the jet at the vena contracta and the area of the orifice is known as the coefficient of contraction. For a sharp orifice, the standard value may be taken as 0611 (concentric with the flow channel). The smaller the value, the greater the influence of the vena contracta.
16. What is metacentre?
Metacentre is the point, about which a floating body begins oscillating when the body is rotated.
17. What is centre of gravity?
The centre of gravity is the point, about which the weight is acting.
18.What is the use of a differential
manometer?
The differential manometer is used to measure the difference between pressure at two points.
19. Define Hydraulic gradient Line
(HGL)?
The Hydraulic Gradient Line or Hydraulic Grade Line (HGL) is defined as a line that joins all the liquid levels indicated throughout the pipeline by piezometers, which is linked to the pipeline. If HGL is above the pipeline centre, the pressure is positive and if HGL is below the pipeline centre, then the pressure is negative. The pressure head and the datum head are represented by HGL.
20. What is the unit of surface tension?
Unit of surface tension is Force/unit length
21. How can you convert one poise into
MKS unit of viscosity?
For the conversion,
The multiplying factor = 0.1
The dividing factor for the conversion is 98.1
22. Define hydrostatic law?
As per the hydrostatic law, the specific weight of the fluid is equal to the rate of increase of pressure in vertical direction.
23. How will you explain the centre of
pressure?
The centre of pressure is the resultant hydrostatic force acting through a point.
24. Which theorems deals with the law of
conservation of energy and law of conservation of mass?
Law of conservation of energy  Bernoulli's theorem
Law of conservation of mass  Continuity
equation
25. What is the use of pelton turbine?
The pelton turbine is used when the head on the turbine is greater than 300 m.
26. Name the fluid, which is
incompressible and nonviscous (in viscid)?
The ideal fluid
27.What is the ratio of dynamic
viscosity to density?
Kinematic viscosity
Kinematic viscosity = dynamic viscosity
/ density
28. How will you measure the discharge
of liquids?
By using a notch.
29. What is the application of a
critical depth meter?
The main application of a critical depth meter is to measure the hydraulic jump.
30. Which force passes through the centroid of the liquid displaced by the
body in a floating body?
The buoyant force.
31. What is the necessary and sufficient
condition for the steady flow?
The necessary condition for the steady flow is that the velocity should be constant at a point with respect to time.
32. What is the use of pilottube?
The main use of pilot tube is to measure the velocity at a particular point.
33. What is the shape of the
stressstrain graph for a Newtonian fluid?
It is a straight line
State
true or false:
34. The convergentdivergent mouthpiece
has maximum coefficient of discharge?
True
35. Water is a Newtonian fluid?
True
36. The similarity of motion signifies
the kinematic similarity between model and a prototype?
True
NOTE:
■ One that has a hydraulic average depth
equal to 1/2 depth is the most economical component of a trapezoidal channel.
■ The pressure head loss for the laminar
flow through pipes varies directly as the velocity varies.
■ In a moving liquid, the forces are
viscous force, gravity force and inertia force.
■ By using Mach number, the model
analysis of aeroplanes and projectiles moving at supersonic speed takes place.
■ When the area of flow increases, then
the velocity also increases for a supersonic flow.
■ One poise = 0.1 Ns/m^{2}
37. Name the flow, if the fluid
particles move in layers parallel to the boundary?
Laminar flow
38. The force exerted by a flowing fluid
on a solid body perpendicular to the direction of flow is termed as?
Lift Force
39. If the surface of the body doesn't
coincide with the streamlines, then the body is termed as?
Bluff Body
40. For a fluid at what condition, the
shear stress becomes zero?
The shear stress becomes zero when the
fluid is at rest
41. Name the point through which the
Buoyant force is acting?
Centre of Buoyancy
42. At what condition, the equilibrium
of a floating body becomes unstable?
when metacentre falls below the centre
of gravity
43. At what condition, the equilibrium
is stable for a submerged body?
When centre of buoyancy falls above the
centre of gravity.
44. When we can say the flow is steady?
If the pressure, density, velocity,
etc.. do not change with respect to time at a particular point, then we can say
that the flow is steady.
45. Distinguish between uniform flow,
compressible flow and laminar flow?
In a fluid flow, if the velocity doesn't
change with respect to the length of direction of flow, then the flow is termed
as uniform flow.
If the density of a fluid varies from
point to point in a flow region, then the flow is termed as compressible flow.
If all the lines are parallel to the
surface and the fluid particles moves in straight lines, then the flow is
termed as laminar flow.
46. What is a turbulent flow?
When the fluid particles moves in a
zigzag way, the flow is termed as turbulent flow.
47. What you know about kinematics of
fluid flow?
Kinematics of fluid flow is the study of
fluid motion without considering the forces causing the flow.
48. which device is used for measuring
the discharge?
Orifice Meter
49. When the mach number becomes less
than unity, the flow is known as?
Subsonic flow
50. How rate of flow is measured?
By using Mouthpieces
51. What is coefficient of velocity?
Coefficient of velocity is defined as
the ratio of actual velocity of a jet of water at venacontracta to the
theoretical velocity.
52. What is inertia force?
Inertia force is the product of mass and
acceleration of a flowing liquid.
53. What you understand about velocity
of approach?
Velocity of approach is the velocity
with which the water approaches a notch.
54. What is the maximum efficiency of
power transmission through a pipe?
66.67%
55. What is the application of bulk
modulus?
For determining the mach number of a
fluid.
56. Write the formula for mach number?
Mach Number = (Inertia Force / Force due to compressibility)^{1/2}
57. What is the use of a Froude number?
Froude number is used for the model
analysis of free surface flows.
58. For what types of fluids, the
boundarylayer takes place?
For real fluids
59. When the Reynolds number is greater
than 5 x 10^{5}, the boundary layer is called as?
Turbulent boundary layer.
60. Where the laminar sublayer exists?
In turbulent boundary layer region
61. In which case, the separation of
boundary layer takes place?
For positive pressure gradient
62. Due to which parameters, the drag
force is exerted by a fluid on a body immersed in the fluid?
Pressure and viscous force
63. At what condition, the flow in open
channel becomes turbulent?
The flow in open channel becomes
turbulent when the Reynolds number is greater than 2000.
64. Differentiate subcritical flow, critical flow and shooting
flow?
When the Froude number in open channel
flow is less than 1.0, then we can say that the flow is subcritical flow.
When the Froude number in open channel
flow is equal to 1.0, then we can say that the flow is critical flow.
When the Froude number in open channel
flow is greater than 1.0, then we can say that the flow is shooting flow.
65. Define specific speed of a turbine?
The specific speed of a turbine can be
defined as the speed of turbine in which the turbine produces unit power at
unit head.
66. Name the device that converts
mechanical energy into hydraulic energy?
Pump
67. Name the device that converts
hydraulic energy into mechanical energy?
Turbine
68. Define a reaction turbine?
If the total energy is kinetic energy
and pressure energy at the inlet of the turbine, then the turbine is called as reaction turbine.
69. Which turbine is a reaction radial
flow turbine?
Francis Turbine
70. Which turbine is an axial flow
reaction turbine?
Kaplan Turbine
71. Which tube is used for discharging
water from the exit of Francis turbine and Kaplan turbine?
Draft Tube
72. Define unit speed of a turbine?
The unit speed of a turbine is the speed
of the turbine, when it is working under unit head.
73. What you understand about curves at
constant head of a turbine?
Main characteristic curves of a turbine
74. What you understand about curves
drawn at constant speed?
Operating characteristic curves of a
turbine
75. Name the curve at constant
efficiency?
Muschel Curves
76. Write the equation of the manometer
head (H_{m}) of a centrifugal pump?
Manometer head (H_{m}) = Total
head at outlet  Total head at inlet
77. For what reason the impellers are
connected in series and parallel?
For producing a high head by multistage
centrifugal pumps, the impellers are connected in series.
For discharging large quantity of liquid
by multistage centrifugal pump, the impellers are connected in parallel.
78. At what condition, cavitation takes
place?
At any point, if the pressure of the
flowing fluid is less than the vapour pressure of the fluid, then cavitation
takes place. Cavitation takes place in case of Francis turbine.
79. Write down the equation for the discharge
through a singleacting reciprocating pump?
Q = ALN/60
80. What is the use of air vessel in
reciprocating pump?
For obtaining a continuous supply of
water at uniform rate.
81. By fitting an air vessel to a double
acting reciprocating pump, the work saves is?
39.2%
82. What is the limiting value of
separation pressure head for water?
2.5 m (abs.)
83. When the separation takes place
during suction stroke and delivery stroke of a reciprocating pump?
At the beginning of suction stroke and
At the end of delivery stroke.
84. What is the use of hydraulic
accumulator?
The hydraulic accumulator is used for
storing the energy of a fluid in the form of pressure energy.
85. What is the working principle of a
hydraulic ram pump?
Waterhammer principle
86. What is the use of a hydraulic
coupling device?
For transmitting same torque to the
driven shaft.
87. What is the use of a torque
converter?
It is used for transmitting increased or
decreased torque towards the driven shaft.
88. Is it possible to adjust the vanes
fixed on the hub in a Kaplan turbine?
Yes. The vanes are adjustable
89. What you know about the runaway
speed of a Pelton wheel?
Runaway speed is the no load speed with
no governor mechanism
90. What is spouting velocity?
Spouting velocity is the ideal velocity
of a jet.
91. What is the use of surge tank in a
pipe line?
For relieving the pressure due to water
hammer, surge tank is used.
92. Which turbine is suitable for low
head and high discharge?
Kaplan Turbine
93. What is free vortex flow?
Free vortex flow can be defined as the
flow of water leaving the impeller in a centrifugal pump casing.
94. What is the use of a rotameter?
The rotameter is used for measuring the
discharge of fluids.
95. What is the use of a hot wire
anemometer?
Hot wire anemometer is used for
measuring the velocity of gases.
96. When the total loss of head is same
as in each pipe?
If the pipes are connected in parallel
97. What is incompressible flow?
From point to point, if the density of a
fluid is constant in a flow region, the flow is called as incompressible flow.
98. What is the equation of the weight
of the body, when a falling body has attained terminal velocity?
Equal to drag force plus the buoyant
force
99. In laminar flow through a circular
pipe, the velocity distribution follows which law?
Parabolic Law
100. Which diagram shows the variations
of pressure head in the cylinder for one complete revolution of crank?
Indicator Diagram
101. Force on the projection of curved surface on a vertical plane for a
submerged surface is indicated by?
Horizontal component of force due to static liquid.