MEASUREMENTS AND THEIR ERRORS Flashcards
SI UNIT MASS
kg
SI UNIT LENGTH
m
SI UNIT TIME
s
SI UNIT TEMPERATURE
K
SI UNIT AMOUNT OF SUBSTANCE
mol
SI UNIT ELECTRICAL CURRENT
A
Tera T
10^12
Giga G
10^9
Mega M
10^6
Kilo k
10^3
Centi c
10^-2
Milli m
10^-3
Micro µ
10^-6
Nano n
10^-9
Pico p
10^-12
Femto f
10^-15
1eV in J
1.6x10^-19J
Precision
Precise measurements are consistent, they fluctuate slightly about a mean value - this doesn’t indicate the value is accurate.
Repeatability
If the original experimenter can redo the experiment with the same equipment and method then get the same results it is repeatable.
Reproducability
If the experiment is redone by a different person or with different techniques and equipment and the same results are found, it is reproducible.
Resolution
The smallest change in the quantity being measured that gives a recognisable change in reading.
Accuracy
A measurement close to the true value is accurate.
Random Errors
Random errors affect PRECISION, meaning they cause differences in measurements which causes a spread about the mean. You cannot get rid of all random errors.
An example of random error is electronic noise in the circuit of an electrical instrument.
Reducing Random Errors
Take at least 3 repeats and calculate a mean, this method also allows anomalies to be identified.
Use computers/data loggers/cameras to reduce human error and enable smaller intervals.
Use appropriate equipment, e.g a micrometer has higher resolution (0.1 mm) than a ruler (1 mm).