Measurements and Errors Flashcards
What are SI units, & name them all.
SI units are fundamental units consisting of mass (kg), length (m), time (s), amount of substance (mol), temperature (K), and electric current (A).
What is 1eV equal to?
1.60x10^-19 J
What is precision?
Consistent measurements about a mean value. Not specifically accurate/close to the true value.
What is accuracy?
Measurements are close to the true value.
What is repeatability?
When the original experimenter can repeat the same experiment and get the same results.
What is reproducibility?
When an experiment can be repeated using different methods, apparatus or experimenters, and get the same results.
What is resolution?
The smallest change in the quantity being measured.
What are random errors, and how can we reduce them?
Random errors affect precision and spread about the mean. They can be reduced by taking repeat measurements (anomalies can be identified), using computers/data loggers/cameras, and using appropriate equipment (higher resolution).
What are systematic errors and how can we reduce them?
Systematic errors affect accuracy, usually due to apparatus or faults in experimental method. Causes results to all be too low/high by the same amount (e.g. zero error, parallax error). They cam be reduces by being aware of the meniscus (read from eye level), background radiation, calibrating apparatus by measuring a known value, and using control variables.
What is uncertainty?
The bounds in which the accurate value can be expected to lie in.
What is a reading + how do we find the uncertainty?
A reading is where one value is observed. Uncertainty is found ±half the resolution.
What is a measurement + how do we find the uncertainty?
A measurement is the difference between two readings. Uncertainty is found ±resolution.
How do we find the uncertainty of digital readings and given values?
±the last significant digit.
How do we find the uncertainty of repeated data?
mean ±range/2
Combining uncertainties
Adding/subtracting: add absolute uncertainties.
Multiplying/dividing: add percentage uncertainties.
Raising to a power: multiply percentage uncertainty by power.
