Physics Flashcards
Beer’s Law
Beer’s law states that the absorption of radiation by a given thickness of a solution of a given concentration is the same as that of twice the thickness of a solution of half the concentration.
Bougner’s (or Lambert’s) Law
Bougner’s (or Lambert’s) law states that each layer of equal thickness absorbs an equal fraction of radiation which passes through it.
Boyle’s Law
Boyle’s law states that at constant temperature the volume of a given mass of gas varies inversely with absolute pressure.
Graham’s Law
Graham’s law states that the rate of diffusion of a gas is inversely proportional to the square root of molecular weight.
Raoult’s Law
Raoult’s law states that the depression or reduction of vapour pressure of a solvent is proportional to the molar concentration of the solute.
Eutectic Mixture
Eutectic mixture is formed by two compounds mixing to produce substance of a single set of physical characteristics. EMLA contains 2.5% lidocaine and 2.5% prilocaine in oil:water emulsion.
Force in base units
m.kg.s-2
Pressure in base units
m-1.kg.s-2
Energy or work in base units
m2.kg.s-2
Power/Watt in base units
m2.kg.s-3
Halothane
Halothane boils at 50°C and has a saturated vapour pressure (SVP) of 32.3 kPa. The SVP is almost identical to isoflurane, and this may allow them be delivered using the same vaporiser, for example, Oxford miniature vaporiser.
All volatile agents inhibit hypoxic pulmonary vasoconstriction and therefore increase shunting.
Halothane sensitises the myocardium to circulating catecholamines and this is one reason why surgeons usually ask the anaesthetist prior to infiltrating epinephrine (adrenaline) containing local anaesthetics.
The minimum alveolar concentration (MAC) of halothane is 0.7%.
Halothane causes less cerebral vasoconstriction than isoflurane, which explains why isoflurane is popular in neuroanaesthesia.
K from Celcius
K = C + 273.15
C from K
C = K - 273.15
What is the Seebeck Effect?
the principle that two different metals in contact generate a voltage, which is temperature dependent
What is a thermopile
Several Thermocouples in series
Tell me about Thermocouples
Found in most thermometers (except those in catheters);
Based on the Seebeck effect that two different metals in contact will generate a voltage which is temperature dependent.
Copper-Constantan is commonly used.
It generates a linear-relationship between Voltage and Temperature.
Tell me about Thermistors
A Thermistor is a type of resistor that has a resistance that changes with temperature.
It allows accurate temperature measurement to an order of 0.1 degrees C.
It is made of semiconductor beads using oxides such as chromium, cobalt, iron, manganese.
A negative temperature coefficient is normally present i.e. as Temperature increases, resistance decreases. However positive temperature coefficients exits.
It shows a non-linear relationship.
Cheap, small, suitable for catheters and oesophageal temp probes.
1 tesla is how many guass
10000
Fully saturated air at 20 degrees C contains how much water?
17g/m3
Fully saturated air at 37 degrees C contains how much water?
44g/m3
Breathing systems filters work on the principles of:
Interception - when a particle following a gas stream around one fibre collides with an adjacent fibre
Inertia - when a particle cannot follow a gas stream around the fibre so impacts against the fibre
Diffusion - when small particles which undergo Brownian motion increasing their probability of striking a fibre
Gravity - when large or heavy particles fall onto fibres as a result of gravity
Electrostatic - when charged air particles are attracted to oppositely charged fibres.
Full cylinder of Oxygen at 15 degrees C has a pressure of:
13700 kpa
Full cylinder of CO2 at 15 degrees C has a pressure of:
5000 kpa (723 psi)
Full cylinder of Entonox at 15 degrees C has a pressure of:
13700 kpa
Full cylinder of Nitrous Oxide at 15 degrees C has a pressure of:
4400 kpa
Full cylinder of Medical Air at 15 degrees C has a pressure of:
13700 kpa
Full cylinder of Cyclopropane at 15 degrees C has a pressure of:
436 kpa
What are the seven base units?
Metre
Second
Kg
Ampere
Kelvin
Candela
Mole
How many litres does a size E oxygen cylinder hold?
680L
How many litres does a size J oxygen cylinder hold?
6800L
Symptoms experienced by different level of currents:
1 mA - tingling pain
5 mA - pain
15 mA - tonic muscular contraction
50 mA - respiratory muscle paralysis
75 mA - ventricular fibrillation.
Force
In physics, a force is an influence that can cause an object to change its velocity, i.e., to accelerate, meaning a change in speed or direction
Mass x Acceleration
Capacitance
Charge / Voltage
Unit of Capacitance is the Farad - 1 Farad is the ability of 1 coloumb of charge to generate a voltage of 1 volt.
Another way of saying this is that, when the voltage across a 1 F capacitor changes at a rate of 1 V/s, the result is a current flow of 1 A.
Kinetic energy
Energy which a body possesses by virtue of being in motion.
1/2 mass x (velocity)2
Tell me the % metabolism for each of the volatile Agents
0.02% Desflurane
0.2% Isoflurane
2% Enflurane
3-6% Sevoflurane
20% Halothane
Paramagnetic Atoms / Gases
Oxygen
Lithium
Calcium
Sodium
Nitric oxide
Magnesium, and
Neodymium.
Diamagnetic Atoms / Gases
Nitrogen
Carbon dioxide, and
Nitrous oxide.
Absolute Humidity
The Mass of Water Vapour present in a particular sample of air at a given temperature. Measured in Kg m-3
Absolute zero
The lowest possible temperature where nothing could be colder and all thermal motion stops.
Precisely 0K or -273.15 degrees C
Ampere A
SI unit of electric current - SI base unit.
The Current that produces a force of 2 x 10-7 Newtons per metre between two parallel wires, of infinite length, 1m apart in a vaccuum.
An equivalent charge to 6.24 x 10^8 electrons (1 coloumb) per second
Boiling point
Temperature at which the vapour pressure of a liquid equals the surrounding ambient pressure and the liquid changes into a vapour.
Calorie
Amount of energy required to increase the temperature of 1g of water by 1 degrees C
Candela
SI unit of luminous intensity
1 cd is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 10^12 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.
A normal candle emits light with a luminous intensity of roughly 1 candela.
Coloumb
The unit of charge.
1 C is the amount of charge passing at a given point per second when 1A current is flowing.
1 C = 1A x 1s
1C is the magnitude of charge possessed by 6.24 x 10^18 electrons.
Critical temperature
The temperature above which a gas cannot be liquefied by pressure alone.
Freezing point
The temperature at which the liquid and solid phases of a substance of specified composition are in equilibrium at a given pressure. A liquid turns in to a solid when it’s temperature is lowered below its freezing point.
Force
That which changes a body’s state of rest or motion.
Derived SI unit - the Newton
1N is the force required to accelerate the mass of 1kg by 1m/s/s.
Force has both magnitude and direction, making it a vector.
Force = mass x acceleration.
Gas
One of the four fundamental states of matter (solid, liquid, gas and plasma).
A substance which is above it’s critical temperature.
It is distinguished from liquids and solids by the vast separation between individual gas particles.
A gas will expand to fill any space available.
Heat capacity
The amount of heat required to raise the temperature of an object by 1 degrees C (specific heat capacity x mass of body)
SI unit of heat capacity = joule per kelvin.
Hertz
Derived SI unit of frequency
1 Hz = 1 cycle per second
Joule
Derived SI unit of energy
1J is the work done (or energy expended) to an object when applying of a force of 1 newton through a distance of 1m.
1J = 1N x 1m or 1 newton metre
Kelvin
SI (base) unit of temperature
1 K = 1/273.16 of the thermodynamic temperature scale, using absolute zero as it’s null point.
1 K = -272.16 degrees C
Kilogram
SI base unit of mass
Standard kilogram is the mass of a cylindrical piece of platinum - iridium alloy kept in Sèvres, France.
Kinetic energy
The energy a body possesses because of it’s motion.
Defined as the energy needed to accelerate the object from a state of rest to it’s given velocity. This energy is equal to the work it would do when decelerating to return to rest.
Latent heat
The energy released or absorbed by a substance when it changes phase at a given temperature, e.g. ice melting.
The term ‘latent’ describes the ‘hidden’ change in energy state, as there is no change in the substance’s temperature during this phase shift.
Latent heat of fusion (melting)
The amount of heat required to convert a unit mass of a solid at it’s melting point into a liquid without an increase in temperature.
Latent heat of vapourisation
The amount of heat required to convert a unit mass of a liquid at it’s boiling point into vapour without an increase in temperature.
Mass
The amount of matter contained in a body.
The SI unit of mass = kilogram
Unlike weight, mass does not alter under conditions of differing gravity.
Metre
SI base unit of length
Since 1983, it is defined as the length of the path travelled by light in vacuum during the time interval of 1/299 792 458 of a second
Mole
SI unit of amount of substance.
Quantity containing the same number of particles as there are atoms in 12g of carbon-12. This number of particles is 6.022 x 10^23 and is known as Avogadro’s constant.
Momentum
Mass x velocity
Newton
Derived SI unit of Force
1 N is the force required to accelerate 1kg by 1m/s/s
Ohm
Derived SI unit of electrical resistance
1 ohm is the resistance between 2 points of a conductor when a constant potential difference of 1 volt applied between them produces a current of 1 ampere.
Pascal
Derived SI unit of pressure
1 Pa is the force of 1 N over 1 m2
pH
The negative logarithm, to the base ten, of the hydrogen ion concentration.
Potential energy
The energy of a body or system as a result of it’s position in an electric, magnetic or gravitational field. IT is the potential of that body to do work.
Power
The rate of doing work.
Unit of power = watt
1 watt = 1 joule per second.
Pressure
Force per unit area
Derived SI unit is the Pascal
Relative humidity
The mass of water in a given volume of air, expressed as a percentage of the maximum mass of water that the air could hold at the given temperature.
The ratio of the water vapour pressure / saturated vapour pressure.
Resistance
The property of a conductor to oppose the flow of current through it (Direct current).
Derived SI unit is ohm.
Saturated vapour pressure
The pressure exerted by a vapour when in contact with and in equilibrium with it’s liquid phase within a closed system at a given temperature.
Second
SI (base) unit of time
Defined according to the frequency of radiation emitted by caesium-122 in its ground state.
Specific heat capacity
The amount of energy required to raise the temperature of 1kg of substance by 1 degrees C.
SHC of water = 4.18 kj/kg degrees C
SHC of human body = 3.5 kj/kg degrees C
Triple point of water
The temperature and pressure at which water exists in equilibrium as liquid water, solid ice and water vapour.
Temperature = 0.01 degrees C or 273.16K, pressure = 0.006 atmospheres.
Vapour
A substance in the gas phase below it’s critical temperature
Volt
Derived SI unit of electrical potential.
1 volt is the potential difference between 2 points of a conducting wire when 1 joule of work is done to move 1 coloumb of charge between them
1 volt is the potential difference between two points of a conducting wire when 1 ampere dissipates 1 watt of power between them
1 volt will ‘push’ a current of 1 ampere through a resistance of 1 ohm.
Watt
Derived SI unit of power
1 watt = 1 joule / s
Weight
The gravitational force acting upon an object
Measured in Newtons
Weight = mass in kg x gravitational acceleration (9.81 m/s/s). A mass of 1 kg will therefore have 9.81N acting on it on the surface of the earth.
What are the base SI units?
Length in m
Mass in kg
Time in s
Current in Ampere
Temperature in Kelvin
Amount of substance in mole
Luminous intensity in candela
What are the derived units?
Area in m2
Volume in m3
Density in kg/cm3
Velocity in m/s
Acceleration in m/s/s
What are the named derived units?
Force in Newton kg x m/s/s
Pressure in Pascal kg/m/s/s
Energy in Joule kg x m^2 /s^2
Power in Watt kg x m^2 / s^3
Electric Charge in Coloumb A x s
Electrical power difference in Volt
Capacitance in Farad
Electrical resistance in Ohm
Magnetic Flux in Weber
Magnetic Flux Density in Tesla
Inductance in Henry
Temperature in Degrees Celcius
