eLFH - SI units Flashcards
Seven fundamental base units from which all other units in the SI system can be derived
SMMACKK
Second (s)
Mole (mol)
Metre (m)
Ampere (A)
Candela (Cd)
Kelvin (K)
Kilogram (Kg)
What is the measure of Seconds
Time
Description of Seconds
Duration of a certain number of oscillations of a Caesium-133 atom
What is the measure of Moles
Amount of a substance
Description of Moles
Amount f substance that contains the same number of particles as 0.012 kg (12g) of Carbon-12
What is the measure of Metres
Length / Distance
Description of Metres
Length travelled by light in a vacuum in 1/3x10^8 of a second
What is the measure of Ampere
Electric current
Description of Ampere
Current in two parallel conductors of infinite length, placed 1 metre apart in a vacuum that would produce force 2x10^-7 N/m
What is the measure of Candela
Intensity of illumination
Description of Candela
Luminous intensity of monochromatic light
What is the measure of Kelvin
Thermodynamic temperature
Description of Kelvin
1 / 273.16 of the thermodynamic triple point of water
What is the measure of Kilogram
Mass
Description of Kilogram
Mass of the prototype kilogram held in Sèvres (in France)
Only physical quantity in the base units - may change as the prototype is slowly degrading
SI unit prefixes to give fraction or multiple of unit
Simple derived SI units
Complex derived SI units
Often given own symbols for simplicity but are derived from base units
Non SI units used in life
Time - Day, Week etc
Volume - Litre
Temperature - degree Celsius
Pressure - Pascal, Bar, mmHg, cmH2O, Atmosphere, PSI
Conversion of degree Celsius to Kelvin
Add 273.15 to Celsius
Eg, 1oC is 274.15 K
Conversion of Litre to cm cubed / m cubed
1 L = 1000 cm3 = 0.001 m3
cm3 = cm cubed
Description of 1 Atmosphere
Atmospheric pressure at sea level
Pressure conversions - all on this flashcard are the same pressure
1 Atmosphere
1.013 Bar
101.3 kPa
101325 Pa
1020 cmH2O
760 mmHg
14.69 PSI
Description of PSI
Pounds per square inch
Rarely clinically relevant
Conversion of mmHg to kPa
Divide mmHg by 7.6 = kPa
(Useful for EtCO2)
Conversion of cmH2O to mmHg
10 cmH2O = 7.6 mmHg
mmHg = cmH2O divided by 0.76
cmH2O = mmHg multiplied by 0.76
