3.1 Measurements and their errors Flashcards
give tera giga mega and kilo units x10*x
T - tera - 12
G - Giga - 9
M - mega- 6
K- Kilo - 3
give centi mili micro nano pico and fempto units x10*x
C - centi - (2)
M- mili - (-3)
µ- micro - (-6)
n - Nano - (-9)
p - pico - (-12)
f - femto - (-15)
how to convert between KWh and Joules
1KwH = 3.6 x 10*6 joules
What is a random and systematic error
Random error has results varying around the true value in an unpredictable way - fixed by repeating
Systematic error has a consistent difference between the measured values and true values
What are precise results
When repeat measurements are consistent/ agree closely to eachother
What is repeatability
How precise repeated measurements are when taken by same person under same conditions w same equipment
What is reproducibility
How precise repeated measurements are when they are taken by different people using different equipment
When is a result accurate
When it is close to the true value
what is resolution
the smallest change in the quantity being measured (input) of a measuring instrument that gives a perceptible change in the reading
absolute uncertainty
Shown as a triangle and its near enough the resolution depending if its a measurement or reading
percentage uncertainty
curly E symbol
absolute uncertainty/ measured value (single value)
for repeated measurements - 1/2range/mean
differrence between a reading and a measurement
reading is off 1 data point - thermometer - uncertainty from 1/2 x resolution
measurement is having to make 2 judgements , more uncertianty , uncertainty at 2 judgements -eg distance between 2 points by taking 2 readings -
ruler uncertainty is resolution
plotting error bars on points on a graph - _
l
_
each side is 0.5x range
worst acceptable line of best fit
using the error bars for a line of best fit
percentage uncertainty for line of best fit gradient
lobf-walobf / lobf x 100 ( positive value)
