3.1 Measurements and their errors Flashcards
(20 cards)
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)
combined uncertainty
for absolute uncertainty add them all
same for percentage uncertainty
if something squared, multiply by 2
if something rooted divide by 2
if something multiplied by 2, uncertainty is unchanged
whats the wavelength range of visible light
380-750 nM
why are repeat readings good
allows anomalies to be identified and discarded
and reduces the effect of random error
ideal voltmeter and ammeter properties
voltmeter infinite resistance
ammeter zero resistance
