1: Measurements and their Errors Flashcards
What are SI units?
The Fundamental (base) units
What are the 6 fundamental units?
Kilogram/Kg (mass), Amperes/A (electric current), Kelvin/C (temperature), Metres/m (length) , Time/s (time) and Moles/Mol (amount of substance).
What is a random error?
An error that affects precision and cannot be completely removed, it causes differences in measurements.
What is a systematic error?
An error that affects accuracy and occurs due to faults in equipment or experimental method, causing the result to be too large/small by the same amount each time.
What are 3 ways to reduce random error?
- take at least 3 repeats and calculate a mean
- use a computer or a data logger
- use higher resolution equipment
How can systematic error be reduced?
Calibrate apparatus before using.
What is precision?
Precise measurements are consistent, they fluctuate slightly about a mean value - this doesn’t indicate the value is accurate.
What is repeatability?
If the original experimenter can redo the experiment with the same equipment and method then get the same results - that is repeatable.
What is reproductibility?
If the experiment is redone by a different person or with different techniques and equipment and the same results are found, it is reproduceible.
What is the standard form for each prefix? Negative
c - x10^-1, d - x10^-2, m - x10^-3, m - x10^-6, n - x10^-9, p - x10^-12, f - x10^-15
What is resolution?
The smallest change in the quantity being measured that gives a recognisable change in reading.
What is an accurate value?
If the value is close to the true value.
What is absolute uncertainty?
uncertainty given as a fixed quantity.
What are the prefixes?
Tera/T, Giga/G, Mega/M, Kilo/k, Centi/c, Deci/d, Milli/m, Micro, Nano/n, Pico/p, Femto/f.
What is the standard form for each prefix? Positive
T - x10^12, G - x10^9, M - x10^6, k - x10^3
