CIE A-Level Physics
Physics Quantities and Units
Physical Quantities and SI Units + Exam Technique
Physical quantities consist of a numerical magnitude and a unit
0s after decimal place are NOT sig figs unless they follow a non-zero digit
Use correct terminology eg. Conductances in parallel add linearly
Never leave answers in fractions
Answer questions with the lowest number of significant figures given in the questions
Fermi questions are where you approximate values as powers of 10
SI base quantities + units:
o Mass, kg
o Length, m
o Time, s
o Current, A
o Tempetature, K
o Amount, mole
Pico (10−12 ¿, nano (10−9 ¿ , micro (10−6 ¿ , milli (10−3 ¿, centi (10−2 ¿, deci (10−1 ¿, kilo (103 ¿,
mega (106 ¿, giga (109 ¿, tera (1012 ¿
Important values: human hearing range – 20 to 20000 Hz, atmospheric pressure - 105 Pa,
distance to sun – 1.5 x 108 m, power of a bulb – 60W
Vocab
Precision – how close measured values are to each other/ a term used to determine the
degree of resolution of a measuring device eg. A stop clock that gives time to two decimal
places of a second has precision of 0.01s; determined by the range in the measurements
Accuracy – how close measured values are to the actual value
Response time – how long it takes for a measurement to display
Sensitivity – the smallest change that an apparatus can detect/ the output of a sensor for
some given input eg. When there is a very small change in input and you get a big change in
output, this is very sensitive equipment
Calibration – are the measurements accurate eg. Is 100V actually 100V?
Resolution – the smallest division you can measure
Stability – does the device give the same measurement every time?
Systematic error – a reproducible inaccuracy; consistently in the same direction
Random error – an error that is unpredictable and can’t be replicated by repeating the
experiment again
Zero error – when an apparatus is not set to 0 before measurement
Human bias – when a person’s processing and interpretation of information affects their
decision and judgements
Parallax – a displacement in the apparent position of an object viewed; must take
measurements at eye level
Drift – measurements may change due to deviations in the measuring instrument after
calibration
Meniscus error – when a measurement is not made from the base of a fluid surface
Physics Quantities and Units
Physical Quantities and SI Units + Exam Technique
Physical quantities consist of a numerical magnitude and a unit
0s after decimal place are NOT sig figs unless they follow a non-zero digit
Use correct terminology eg. Conductances in parallel add linearly
Never leave answers in fractions
Answer questions with the lowest number of significant figures given in the questions
Fermi questions are where you approximate values as powers of 10
SI base quantities + units:
o Mass, kg
o Length, m
o Time, s
o Current, A
o Tempetature, K
o Amount, mole
Pico (10−12 ¿, nano (10−9 ¿ , micro (10−6 ¿ , milli (10−3 ¿, centi (10−2 ¿, deci (10−1 ¿, kilo (103 ¿,
mega (106 ¿, giga (109 ¿, tera (1012 ¿
Important values: human hearing range – 20 to 20000 Hz, atmospheric pressure - 105 Pa,
distance to sun – 1.5 x 108 m, power of a bulb – 60W
Vocab
Precision – how close measured values are to each other/ a term used to determine the
degree of resolution of a measuring device eg. A stop clock that gives time to two decimal
places of a second has precision of 0.01s; determined by the range in the measurements
Accuracy – how close measured values are to the actual value
Response time – how long it takes for a measurement to display
Sensitivity – the smallest change that an apparatus can detect/ the output of a sensor for
some given input eg. When there is a very small change in input and you get a big change in
output, this is very sensitive equipment
Calibration – are the measurements accurate eg. Is 100V actually 100V?
Resolution – the smallest division you can measure
Stability – does the device give the same measurement every time?
Systematic error – a reproducible inaccuracy; consistently in the same direction
Random error – an error that is unpredictable and can’t be replicated by repeating the
experiment again
Zero error – when an apparatus is not set to 0 before measurement
Human bias – when a person’s processing and interpretation of information affects their
decision and judgements
Parallax – a displacement in the apparent position of an object viewed; must take
measurements at eye level
Drift – measurements may change due to deviations in the measuring instrument after
calibration
Meniscus error – when a measurement is not made from the base of a fluid surface
