Download Theory

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Viscosity
Determination of a given liquid viscosity
Object :
to determine of a given liquid viscosity using the falling ball method
Theory
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear
stress or tensile stress. In everyday terms (and for fluids only), viscosity is "thickness" or
"internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick",
having a higher viscosity. Put simply, the less viscous the fluid is, the greater its ease of
movement (fluidity
With the exception of superfluids, all real fluids have some resistance to stress and therefore
are viscous. A fluid which has no resistance to shear stress is known as an ideal fluid or
inviscid fluid. In common usage, a liquid with the viscosity less than water is known as a
mobile liquid, while a substance with a viscosity substantially greater than water is simply
called a viscous liquid.
The study of flowing matter is known as rheology, which includes viscosity and related
concepts.
If a ball with density  (kg/m3) moves with a constant terminal velocity v (m/s) in a
liquid of density ' (kg/m3), as shown in the figure. Then, the sum if the forces acting on the
ball equal zero. Therefore total upright forces and downright forces have to be the same.
Buoyant force + Friction force
Gravitational Force
Gravitational force =
Buoyant force + Friction force
-2-
Gravitational Force
=
mg
Buoyant Force
=
4
3
Friction Force
=
fv
=
4
3
𝜋 𝑅 3 𝜌𝑔
𝜋 𝑅 3 𝜌′ 𝑔
=
6 RV
Where
 : viscosity coefficient of the liquid in (Pa.s.)
R : radius of the ball
f : friction coefficient
SO,
4
3
𝜋 𝑅 3 𝜌𝑔
4
3
=
𝜋 𝑅 3 𝜌′ 𝑔 + 6 RV
By calculation :

=
𝟐𝒈𝑹𝟐
(
𝟗𝒗
) (𝝆 − 𝝆′ )
Pa.s.
Procedure
1- Measure the temperature of the liquid by using of the thermometer fixed in the
outer tube
2- Measure the radius of the ball (R) by using of micrometer (repeat three times)
3- Measure the time the ball need to fall a distance 10 cm and then calculate the
velocity v (m/s)
(repeat three times)
3
4- Givens : density of the boron-glass ball  = 2200 kg/m
the density of a 40 % sugar solution ' = 1180 kg/m3.
Gravity = 9.8 m/s2
5- The tube filled with the liquid is titled by an angle of 10°, therefore the viscosity
coefficient will be calculated from the relation :
𝟐
 = (𝟐𝒈𝑹
) (𝝆 − 𝝆′ ) cos 10
𝟗𝒗
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Pa.s.
Inverse Sqaure Law (ISL)
Object :
to verify of the inverse square relation between distance and intensity of
radiation
Theory
An inverse-square law is any physical law stating that a specified physical
quantity or intensity is inversely proportional to the square of the distance from the
source of that physical quantity. In equation form:
The divergence of a vector field which is the resultant of radial inverse-square law fields
with respect to one or more sources is everywhere proportional to the strength of the
local sources, and hence zero outside sources. Newton's law of universal gravitation
follows an inverse-square law, as do the effects of electric, magnetic, light, sound, and
radiation phenomena.
In radiation, as you double the distance
between source and detector, intensity
of radiation goes down by a factor of
four. If you triple the distance, intensity
will go down by a factor of nine. If you
quadruple the distance, the intensity will
go down by a factor of
sixteen.
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Procedure
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Set the voltage of the GM tube to the optimal operating voltage (around 900 V)
From the Preset menu, set Runs to Zero and set Preset Time to 10 sec.
First do a run without radioactive sources to check your background level.
Place a radioactive source in the top shelf (2 cm from GM actual detector) and
begin taking data
5- Move the source down one shelf each time and take another run. You should
see the data accumulating in the data window
1
6- Plot a graph between R (count rate) and the inverse square of the distance (𝑑2 )
7- Examine the plot shape to verify the fact of inverse square law (straight line)
R
𝟏
𝐝𝟐
R1
R2
R3
R (average)
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d
𝟏
𝒅𝟐
Attenuation Coefficient
Object :
to investigate the attenuation of x-rays as a function of the absorber thickness
Theory
Attenuation is the gradual loss in intensity of any kind of flux through a medium.
For instance, sunlight is attenuated by dark glasses, X-rays are attenuated by
lead, and light and sound are attenuated by water.
When x-rays fall on a material, rays may suffered from scattering and
absorption. The scattering of x-ray quanta at the atoms of the attenuator
material causes a apart of the radiation to change direction. This reduces the
intensity in the original direction. This scattering can be either elastic or entail an
energy loss or shift in wavelength i.e. inelastic scattering.
Intensity of x-ray beam passing through matter of constant density and
composition decreases exponentially as function of distance traveled. The X-ray
intensity transmitted through a dense material is given by :
I = Io exp (-x)
where I is the transmitted X-ray intensity, I0 is the incident X-ray intensity, μ is
the linear
attenuation coefficient (in cm-1) and x is the thickness of the material (in cm).
This equation shows
that the X-ray intensity depends on the
− the density of the material (the linear attenuation coefficient μ increases with
density)
− the thickness of the material
I
The greater the so-called transmittance I of an attenuator is, the lower is
o
its attenuating capacity. If we assume that the properties of the incident
radiation remain unchanged in spite of attenuation, an increase in the thickness
X by the amount dX will cause a decrease in the transmittance T by the amount
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dT. The relative reduction in transmission is proportional to the absolute
increase in thickness.
−
dT
T
= 𝜇. 𝑑𝑋
The relation between the linear attenuation coefficient of a material and the attenuator
thickness is known as Lambert's law.
Procedure
1- Set the tube high voltage to U = 21 kv
2- Set the emission current i = 0.05 mA
3- Press the key TARGET
4- Set the angular step width  β = 0°
5- Set the measuring time t = 30 sec.
6- Using the adjust knob, set the angular positions of the absorbers (approximately,
0°, 10°, 20°, 30°, 40°, 50° and 60°) one after another, start the measurement
with the scan key and display by pressing REPLAY, write your experiment result
-7-
Elctro Cardio Gram (ECG)
Object :
to record and analyze the electrocardiogram (ECG) signals
Theory
Electrocardiography is a trans-thoracic (across the thorax or chest) interpretation of the
electrical activity of the heart over a period of time, as detected by electrodes attached to the
outer surface of the skin and recorded by a device external to the body. The recording
produced by this noninvasive procedure is termed as electrocardiogram (also ECG or EKG).
An ECG test records the electrical activity of the heart.
ECG is used to measure the rate and regularity of heartbeats, as well as the size and
position of the chambers, the presence of any damage to the heart, and the effects of drugs or
devices used to regulate the heart, such as a pacemaker. Most ECGs are performed for
diagnostic or research purposes on human hearts, but may also be performed on animals,
usually for diagnosis of heart abnormalities or research.
An ECG is the best way to measure and diagnose abnormal rhythms of the heart,
particularly abnormal rhythms caused by damage to the conductive tissue that carries
electrical signals, or abnormal rhythms caused by electrolyte imbalances. In a myocardial
infarction (MI), the ECG can identify if the heart muscle has been damaged in specific areas,
though not all areas of the heart are covered. The ECG cannot reliably measure the pumping
ability of the heart, for which ultrasound-based (echocardiography) or nuclear medicine tests
are used. It is possible for a human or other animal to be in cardiac arrest, but still have a
normal ECG signal (a condition known as pulseless electrical activity).
The ECG device detects and amplifies the tiny electrical changes on the skin that are
caused when the heart muscle depolarizes during each heartbeat. At rest, each heart muscle
cell has a negative charge, called the membrane potential, across its cell membrane.
Decreasing this negative charge towards zero, via the influx of the positive cations, Na + and
Ca++, is called depolarization, which activates the mechanisms in the cell that cause it to
contract. During each heartbeat, a healthy heart will have an orderly progression of a wave of
depolarisation that is triggered by the cells in the sinoatrial node, spreads out through the
atrium, passes through the atrioventracular node and then spreads all over the ventricles. This
is detected as tiny rises and falls in the voltage between two electrodes placed either side of
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the heart which is displayed as a wavy line either on a screen or on paper. This display
indicates the overall rhythm of the heart and weaknesses in different parts of the heart muscle.
Usually, more than two electrodes are used, and they can be combined into a number of pairs
(For example: left arm (LA), right arm (RA) and left leg (LL) electrodes form the three pairs
LA+RA, LA+LL, and RA+LL). The output from each pair is known as a lead. Each lead
looks at the heart from a different angle. Different types of EKGs can be referred to by the
number of leads that are recorded, for example 3-lead, 5-lead or 12-lead ECGs (sometimes
simply "a 12-lead"). A 12-lead EKG is one in which 12 different electrical signals are
recorded at approximately the same time and will often be used as a one-off recording of an
ECG, traditionally printed out as a paper copy. Three- and 5-lead ECGs tend to be monitored
continuously and viewed only on the screen of an appropriate monitoring device, for example
during an operation or whilst being transported in an ambulance. There may or may not be
any permanent record of a 3- or 5-lead ECG, depending on the equipment used.
The term "lead" in electrocardiography causes much confusion because it is used to
refer to two different things. In accordance with common parlance, the word lead may be used
to refer to the electrical cable attaching the electrodes to the ECG recorder. are standard in a
"12-lead" ECG.
Alternatively, the word lead may refer to the tracing of the voltage difference
between two of the electrodes and is what is actually produced by the ECG recorder. Each
will have a specific name. For example "lead I" is the voltage between the right arm electrode
and the left arm electrode, "Lead II" is the voltage between the right arm and the feet,
whereas, Lead II is the voltage between the left arm and the feet.
LEAD I
LEAD II
LEAD III
=
=
=
RA-LA
RA-LL
LA-LL
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Feature
RR
interval
P wave
PR
interval
PR
segment
Description
The interval between an R wave and the next R wave: Normal resting
heart rate is between 60 and 100 bpm.
During normal atrial depolarization, the main electrical vector is directed
from the SA node towards the AV node, and spreads from the right atrium
to the left atrium. This turns into the P wave on the ECG.
The PR interval is measured from the beginning of the P wave to the
beginning of the QRS complex. The PR interval reflects the time the
electrical impulse takes to travel from the sinus node through the AV node
and entering the ventricles. The PR interval is, therefore, a good estimate
of AV node function.
The PR segment connects the P wave and the QRS complex. The impulse
vector is from the AV node to the bundle of His to the bundle branches
and then to the Purkinje fibers. This electrical activity does not produce a
contraction directly and is merely traveling down towards the ventricles,
and this shows up flat on the ECG. The PR interval is more clinically
relevant.
QRS
complex
The QRS complex reflects the rapid depolarization of the right and left
ventricles. They have a large muscle mass compared to the atria, so the
QRS complex usually has a much larger amplitude than the P-wave.
J-point
The point at which the QRS complex finishes and the ST segment begins,
it is used to measure the degree of ST elevation or depression present.
ST
segment
The ST segment connects the QRS complex and the T wave. The ST
segment represents the period when the ventricles are depolarized. It is
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Duration
0.6 to 1.2s
80ms
120 to
200ms
50 to 120ms
80 to 120ms
N/A
80 to 120ms
isoelectric.
T wave
ST
interval
QT
interval
U wave
J wave
The T wave represents the repolarization (or recovery) of the ventricles.
The interval from the beginning of the QRS complex to the apex of the T
wave is referred to as the absolute refractory period. The last half of the T
wave is referred to as the relative refractory period (or vulnerable period).
160ms
The ST interval is measured from the J point to the end of the T wave.
320ms
The QT interval is measured from the beginning of the QRS complex to
the end of the T wave. A prolonged QT interval is a risk factor for
ventricular tachyarrhythmias and sudden death. It varies with heart rate
and for clinical relevance requires a correction for this, giving the QTc.
Up to 420ms
in heart rate
of 60 bpm
The U wave is hypothesized to be caused by the repolarization of the
intervenqctricular septum. They normally have a low amplitude, and even
more often completely absent. They always follow the T wave and also
follow the same direction in amplitude. If they are too prominent, suspect
hypokalemia, hypercalcemia or hyperthyroidism usually.
The J wave, elevated J-point or Osborn wave appears as a late delta wave
following the QRS or as a small secondary R wave. It is considered
pathognomonic of hypothermia or hypocalcemia.
Procedure :
1- Test subject has to be relaxed and in a resting position, as otherwise the ECG
signal can be overlaid by the electrical potentials of the skeletal musculature,
falsifying the measurement.
2- To reduce the skin resistance, spread electrode gel on the electrodes and attach
them to the appropriate points in the body using the rubber straps.
3- Then, attach the leads to the electrodes as follow
i. Red right arm
ii. Yellow left arm
iii. Green left arm
iv. Black right arm
4- Clean the electrodes after each use with a paper towel or similar to prevent a salt
layer from forming when the gel dries. Then, spray the electrodes and the
corresponding skin sites with disinfectant to ensure maximum hygiene.
Examination starting
5- Load settings
6- Start the measurement (F9)
7- The three leads according to Einthoven are recorded simultaneously
8- Stop the measurement with (F9)
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Lung Volume (Respirometer)
Object :
to measure the lung parameters to verify the respiration efficiency
Theory
A respirometer is a device used to measure the rate of respiration of a living organism by
measuring its rate of exchange of oxygen and/or carbon dioxide. They allow investigation
into how factors such as age, chemicals or the effect of light affect the rate of respiration.
Respirometers are designed to measure respiration either on the level of a whole animal
(plant) or on the cellular level. These fields are covered by whole animal and cellular (or
mitochondrial) respirometry, respectively.
The traditional respirometer is used to measure the lung performance parameters.
Respiration parameters
Tidal Volume
TV
Volume of air inspired and then expired during breathing in rest
Inspiratory Reserve Volume
IRV
Volume of air a person can inspire above tidal volume
Expiratory Reserve Volume
ERV
Volume of air a person can exhale below resting expiratory volume
Inspiratory Capacity
IC
Volume of a person can inspire above the resting expiratory volume
Residual Volume
RV
Volume of air left in lung after maximum expiratory effort
Functional Residual Capacity
FRC
Air remains in lung after normal expiration
Vital Capacity
VC
Maximum volume of air that can be inspired and then expired
Forced Vital Capacity
FVC
The same VC but under maximum expiratory force
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Respiratory Volumes and Capacities
This is the area of the respiratory system (trachea
Anatomic Dead Space
and bronchi) in which air is not exposed to blood.
(150 cm3)
Physiological Dead Space
This
is the area of alveoli by act of some diseases
cannot perfuse the blood to O2.
Procedure
1- Connect the spirometer box to Sensor-Cassy input A about 10 seconds before
the measurement (warm-up phase). Use a new mouthpiece and a new bacteria
filter for every test person and disinfect the sieves regularly with a
disinfectant.
2- Load settings
i. Compensate the zero point off the displayed volume flux
dVA1. Open the window settings volume flux dVA1, select -0and make sure that no air is flowing through the spirometer
during this procedure.
ii. Start the measurement as soon as possible afterwards with F9
(as long as the thermal error in volume flux dVA1 is still
negigble)
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iii. Breathe evenly through the spirometer three or four times. Then
inhale and exhale as much air as possible through the
spirometer. Then breathe evenly again.
iv. Stop the measurement with F9.
Evaluation
The tidal volume V1 is the difference between the maximum and minimum for
normal breathing. You can determine this e.g. by setting horizontal lines or directly by
measuring the difference. You can insert this value at any point in the diagram as text.
The vital capacity V2 is calculated as the sum if the inspiratory and expiratory
reserve volume and the tidal volume. It can be determined from the minimum and
maximum at maximum inspiration and expiration analogous to the tidal volume.
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Human Eye Model
Object :
to
Theory
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