Practical Skills Y1 Flashcards
List all seven base quantities and their abbreviations?
length - l, s, d;
time - t;
temperature - T;
mass m
amount of substance n;
electrical current I;
Luminosity L
List all seven SI units and their symbols
Kilograms - kg
Metre - m
Seconds - s
Kelvin - K
Ampere - A
Mole - mol
Candela - cd
Uncertainties Adding or subtracting
sum of absolute uncertainties
Uncertainties Multiplied or divided
sum of percentage uncertainties
Accuracy
if the results are very close to the accepted value
Precision
The spread of repeated results - repeat results are very similar
What is the correlation between precision and percentage uncertainty
the more precise the results the smaller the percentage uncertainty
What is the reliability of an experiment?
Give consistent results each time the experiment is repeated - reliable results produce small scatter graphs
What is resolution
smallest divisions on the measuring instrument
How to calculate % difference
(measured value - true value)/truevalue * 100
How to draw the line of worst fit?
add in the error bars - draw the line of worst fit by joining the bottom of the first error bar and the top of the last
What are lines of worst fit used for?
To find the percentage uncertainty of the gradient
How can random error be reduced?
repeating the measurements/experiments and calculating a mean
What does repeating, and calculating a mean do in terms of error?
reduces random error
What is a systematic error?
an error where the measured value deviates from the actual value by the same amount consistently
(eg zero error)
What is random error?
errors in measurement caused by factors which vary with each measurement
(eg parallax error)
When calculating averages with a table of given values what do you do to outliers?
IGNORE THEM
How to convert squared and cubed prefixes to si? (you can use 1cm^3 as an example??
convert the prefix to a power, than multiply by the original power attached to the si unit;
In the case of 1cm^3 becomes x10^-6m^3 “
When talking about precisions, how do you make a measurement more precise?
use instruments with greater resolution
How do you make an experiment more reliable?
repeat and calculate a suitable mean
Absolute uncertainty of a micrometer?
0.01mm
Absolute uncertainty of a ruler?
0.001m (1mm)
When asked to plot something, what must be done?
plot crosses as well as line/curve of best fit (same number of points either side of line of best fit)
How to calculate an absolute uncertainty?
take the range of values given and divide by 2
