Physics Flashcards
Accuracy
The ability of a measurement device to match the actual value of the quantity being measured
Precision
The reproducibility of repeated measurements and a measure of their likely spread
Drift
A fixed deviation from the true value at all points in the measured range. Can be corrected by zeroing (improving accuracy)
Hysteresis
The phenomenon by which a measurement varies from the input value by different degrees on whether the input variable is increasing of decreasing in magnitude at that moment in time
Base SI Units
SMMACKK
Second (time) Meter (distance) Mole (amount) Ampere (current) Candela (luminous intensity) Kilogram (mass) Kelvin (temperature)
Second
S
Time
The duration of a given number of oscillations of the caesium-133 atom
Meter
M
Distance
The length of the path travelled by light in a vacuum during a certain fraction of a second (1/299792458)
Mole
Mol
Amount
The amount of a substance which contains as many elementary particles as there are atoms in 12g of carbon-12 (6.022 x 10^23)
Ampere
A
Current
The current that produces a force of 2x10^-7 newtons per meter between 2 parallel wires of infinite length, 1m apart in a vacuum
1 ampere = equivalent charge to 6.24x10^18 electrons (1 coloumb) per second
Candela
CD
Luminous intensity
1cd is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540x10^12 Hz and has radiant intensity in that direction of 1/683 watt per steradian
Kilogram
Kg
Mass
The mass of the international prototype of the kilogram held in Sevres, France
Only base SI unit with a SI prefix
Kelvin
K
Temperature
1/273.16 of the thermodynamic temperature of the triple point of water
1 atmosphere
101.3 kPa 1 bar 14.69psi 1020 cm H2O 30 inches of Hg 760mmHg
Absolute humidity
kg/m^-3
The mass of water vapour present in a particle sample of air at a given temperature
Relative humidity
The mass of water in a given volume of air, expressed as a % of the maximum mass of water that the air could hold at the given temperature
= the ratio of the water vapour pressure to the SVP
Boiling Point
The temperature at which the vapour pressure of a liquid equals the surrounding ambient pressure and the liquid changes to a vapour
Calorie
The amount of energy required to increase the temperature of 1g of H20 by 1 K 1 calorie (little c) = 4.16 joule Kcalorie = 1 large calorie (capital C) or 1000c or 4.16kJ
Coloumb
C Unit of charge 1 C = the amount of charge passing a given point per second, when 1 ampere of current is flowing 1 C = 1 A x 1 sec 1C = charge of 6.24 x 10^18
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
Force
Newton
That which changes a body’s state of rest of motion
1N = the force required to accelerate a 1kg mass at a rate of 1m per second squared
Force is a vector - has both magnitude and direction
Force = mass X acceleration
Heat Capacity
The amount of heat required to raise the temperature of an object by 1 degree
SI unit of heat capacity = joule per kelvin
Specific heat capacity
Heat capacity X mass of body
Hertz
Hz
Derived SI unit of frequency
1 Hz = 1 cycle per second
Joule
Derived SI unit of energy
1J = the work done to an object when applying of a force of 1 newton through a distance of 1m
1 J = 1 N x 1 m
Kinetic energy
The energy a body possesses because of it motion
The energy required to accelerate the object from a state of rest to its given velocity
Latent heat
The energy release or absorbed by a substance when it changes phase at a given temperature
‘latent’ because ‘hidden’ change in energy as there is no actual change in temperature during the phase shift
Latent heat of fusion
Amount of heat required to convert a unit mass of a solid at its melting point into a liquid without an increase in temperature
Latent heat of vaporisation
The amount of heat required to convert a unit mass of a liquid at its boiling point into a vapour without an increase in temperature
Mass
SI unit = kg
amount of matter contained in a body
Doesn’t change with differing gravity
Momentum
Mass X Velocity
Newton
Derived unit of force
1N = force required to accelerate a mass of 1kg by 1m/s/s
Ohm
Derived unit of electrical resistance
1 ohm is the resistance between 2 points of a conductor when constant potential difference of 1 volt applied between them produces a current of 1 ampere
Pascal
Pa
Force of 1N acting over 1m squared
pH
Negative logarithm to the base 10 of the hydrogen ion concentration in a solution
pH = -log10[H+]
Electrocution
1-5mA = tingling sensation 5-10mA = pain 15mA = 'can't let go' threshold 50mA = respiratory arrest 100mA = VF
Class 1 electrical equipment
Accessible conductive parts (e.g. the case) are connected to earth by an earth wire which maintains the exposed metalwork at zero potential and provides a low resistance path for current to return to the local electricity substation in the event of a fault
Class 2 electrical equipment
Class II equipment is protected by double or reinforced insulation. There is minimal chance any person could come into contact with a faulty live component therefore an earth wire is not required.
Class 3 electrical equipment
Powered internally by a battery or SELV (safety extra low voltage)
SELV = Voltage not greater than 25 V AC
or 60 V DC; No earth connection (usually floating circuit); Low risk of accidental contact with higher voltage
Microshock
Microshock may occur when the skin is breached if unwanted or aberrant currents are delivered directly to the myocardium. In this case, by generating higher current densities near the myocardium currents as low as just 100 μA can cause dangerous dysrhythmias.
Unlikely to occur
Type B Electrical Equipment
Logo = man Can be class 1, 2 or 3 Not suitable for direct connection to patient Max leakage current: - Type 1 =
Type BF Electrical Equipment
Logo = man in box Can be class 1, 2 or 3 Floating circuit so suitable for direct connection to patient Max leakage current: (same as type B) - Type 1 =
Type CF Electrical Equipment
Logo = heart in box Can be class 1, 2 or 3 High degree of protection of shock so suitable for direct cardiac connection Max leakage current: - NC =
Diathermy
High Frequency AC
H (heating effect) = current squared x area
Current density = current flowing per unit area
Heating effect proportional to current density
High frequency currents used to reduce dysrhythmias
Monopolar = 100-200W
Bipolar = 100W)
Coagulation = interrupted current, lower freq (250-400KHz), high voltage (up to 9kV), lower power (
SVP
Saturated Vapour Pressure
The pressure exerted by a vapour when in contact with and in equilibrium with its liquid phase within a closed system, at a set temperature.
Affected by temperature ONLY, not affected by pressure
Max SVP in open container at sea level is 1 atm
Colligative properties
Properties of a solution that depend on the number of particles dissolved in a solvent (depend on osmolality)
Freezing point reduced (with increased solute)
SVP reduced (reduced surface area)
Boiling point increased
Osmotic pressure increased
Scavenging pollutant levels
N20 = 100ppm Halothane = 10ppm Isoflurane = 50ppm Enflurane = 50ppm Sevoflurane = 20ppm Desflurane = no data 8 hour time weighted average
Clarke polarographic electrode
Oxygen measurement Ag/AgCl anode Platinum cathode KCl solution 0.6V applied
Galvanic fuel cell
Oxygen measurement Gold cathode Lead anode KOH solution Generates own voltage
Mass spectroscopy
Can measure all gases/volatiles
Can’t differentiate same MW
