physics 3 Flashcards
what is the unit of radioactivity?
The unit to measure radioactivity is the Becquerel.
definition: a given quantity of radioactive substance has the activity of one Becquerel if the disintegration of one nucleus occurs on average every second.
This is an exponential process, with rate of decay depending on the amount of radioactive isotope present
Gamma (y) radiation has very high frequency and energy.
what is the Finapres device
-volume clamp method of Peñáz,
-finger cuff is used to apply a counter-pressure that changes with the arterial pressure.
-This counter-pressure is controlled so that the blood volume in the finger arteries remains constant, as measured by an infrared plethysmograph. This method allows for continuous, non-invasive monitoring of the blood pressure.
What is a resistor?
essential electrical component used to control flow of current by providing resistance
what is a capacitor?
a capacitor is an electrical component that stores charge in the form of an electrostatic field and is the key component of a cardiac defibrillator. It consists of two metal plates separated by insulator (dielectric). Capacitance is measured in farads (typically μF, pF or nF). 1 farad = potential difference of 1 volt across plates. Capacitors are used to ‘smooth out’ rectified AC voltage to produce battery-like DC voltage. Capacitors do not directly convert AC to DC.
what is a diode?
a diode allows current to flow in one direction only. This is essential in rectifying circuits where AC is converted to DC, and in protecting circuits by blocking reverse currrent.
what does an inductor do?
An inductor stores energy in a magnetic field when current flows through it and resists changes in the current.
What is a transformer?
A transformer is used to increase or decrease voltage in an AC circuit, and transfers electrical energy between two or more circuits through electromagnetic induction but does not directly control the flow of current.
whats the accuracy of pulse oximeters?
+/- 2% within range of 70-100%
other causes for error:
-Methaemoglobin
-carboxyhaemglobin
partial pressure of O2 agains sats is sigmoid.
what occurs when different mA pass through the body
1 mA- tingling
10mA muscle contractions and ‘no let go’ in some individuals
100mA- VF
1A- severe burns and muscle contractions, immediate organ damage
10A severe burns, immediate cardiac arrest due to massive thermal and physiological damage often bypassing the fibrillation phase
what is bernoull’is principle
Bernoulli’s principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid’s potential energy. It is the simultaneous increase in speed and kinetic energy and fall in pressure that causes entrainment of large volumes of air into a flow of 100% oxygen into the nozzle of HAFOE masks.
what is the venturi effect
The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constriction in a tube.
what is the coanda effect
The Coanda effect is a situation in which a flow of gas or liquid attaches itself to a nearby surface and remains attached even when the surface curves away from the initial direction of flow. e.g water and spoon
what material is commonly used for piezoelectric crystals
Lead zirconate titanate (PZT) is the most commonly used synthetic piezoelectric material in ultrasound transducers to convert electrical energy into sound waves and vice versa
Quartz is a naturally occurring piezoelectric material but not commonly used in modern ultrasound transducers.
how much does pressure increase by when diving
for every 10metres below water, pressure increases by 1 atmospheres
sea level=1 atm
10 below =2 atm
20 =3
30-4atm
e.g 30metres below waters surface is 4 atm
ideal gas law/equation
PV=nRT
P=pressure
V=volume
n=number of moles
R=ideal gas constant
T=Temp
If we increased number of moles, this would be an equal increase in pressure (e.g if you added 20g if nitrogen to a sealed box)
moles=mass of substance/molar mass
N=14molar mass
N2 therefore is 28
20/28 is 0.714
therefore the pressure in the box would increase by approx 0.71 units assuming ideal gas behavious and constant volume and temp
how to calculate number of moles
moles = mass of substance/ molar mass
e.g if you have 20g of nitrogen
N molar mass=14
N2=28
moles= 20/28= 0.714moles
what is the molar mass of common anaes gases
N=14
N2=28
O=16
O2=32
C=12
H=1
H2=2
H2O= 18
CO2=44
Nitrous oxide (N₂O): 44.01 g/mol
Oxygen (O₂): 32.00 g/mol
Nitrogen (N₂): 28.02 g/mol
Carbon dioxide (CO₂): 44.01 g/mol
Sevoflurane (C₄H₁₂O₂): 200.06 g/mol
Isoflurane (C₆H₂Cl₂F₃O): 184.50 g/mol
Desflurane (C₆H₁₂F₆O): 168.04 g/mol
Halothane (C₂HBrClF₃): 197.40 g/mol
Xenon (Xe): 131.29 g/mol
Helium (He): 4.00 g/mol
how to convert celcius to kelvin?
add 273.15
e.g 50 degrees=> 50+273.15= 323.15K
what is atm at 5000m above sea level
0.54 atm
Pressure decreases above sea level and decreases below
as a gen rule pressure drops by 0.12 bar for every 1000m above sea level
Comparison of Atmospheric Pressure:
Sea Level (0 m) → 1.00 atm (101.3 kPa)
Kilimanjaro (5,895 m) → ~0.47 atm (47 kPa)
Mount Everest (8,848 m) → ~0.33 atm (33 kPa)
e.g
What are units of pressure?
kg.m^-1.S-2
P=F/A
whats the difference between gauge and atomspheric pressure?
gauge pressure is what is rad on gauge e.g in a full cylinder 137 bar/ 13,700 kPa..
gauge will read 0 when cylinder is empty which is incorrect as 1 atm remains.
absolute pressure= total in cylinder + atmospheric (1 bar
=137+1= 138 bar
