Wokring as a physicist Flashcards
What are S.I base units?
The S.I is a globally agreed system of units, with sevens base quantities:
Kilograms, meters , seconds, cd, moles, kelvin, Amps
Define validity?
A measurement is valid if it measures what it is supposed to be measuring- this depends on both the method and the instruments
Define true value?
The value that would have been obtained in an ideal measurement.
Define accuracy?
A measurement result is considered to be accurate if it is judged to be close to the true value.
Define precision?
A quality denoting the closeness of agreement (consistency), between values obtained by repeated measurement. It is precise if the values cluster together closely together.
Define Repeatability?
The precision obtained when measurement results are obtained by a single operator using a single method over a short timescale.
Define reproducibility?
The precision obtained when measurement results obtained by different operators using different pieces of apparatus.
Define uncertainty?
The interval within which the true value can be considered to lie with a given level of confidence or probability.
Define error?
The difference between the measurement result and the true value, if a true value is thought to exist.
Define resolution?
The smallest measuring interval and the source of uncertainty in a single reading.
What are random errors?
Errors of measurement in which the measured quantities differ from the mean value with different magnitudes and directions
What are systematic errors?
Errors of measurement in which the measured quantities differ from the true value by a fixed magnitude and same direction
Formula for uncertainty with 1 variable?
(uncertainty/measured value) x value
Formula for uncertainty with several measurements?
((Range/2)/mean) x 100
Uncertainties for meter ruler, digital calipers, and micrometers?
Meter ruler: 0-1000mm / +- 1mm
Digital caliper: 0-150mm / +- 0.01 mm
Micrometer: 0-25mm / +- 0.01 mm
