Measurements and their errors Flashcards
1
Q
T prefix
A
10^12
2
Q
G prefix
A
10^9
3
Q
M prefix
A
10^6
4
Q
k prefix
A
10^3
5
Q
m prefix
A
10^-3
6
Q
micro prefix
A
10^-6
7
Q
n prefix
A
10^-9
8
Q
p prefix
A
10^-12
9
Q
f prefix
A
10^-15
10
Q
SI unit for mass
A
kg
11
Q
SI unit for length
A
metres
12
Q
SI unit for time
A
seconds
13
Q
SI units for temperature
A
kelvin
14
Q
SI unit for amount of a substance
A
Moles
15
Q
SI unit for current
A
Amps
16
Q
Alternative unit for joules
A
eV and kWh
17
Q
What is an eV
A
Electron volt - energy required to accelerate an electron from rest through a pd of 1 volt
18
Q
How many joules in an eV
A
1.6 x 10^-19
19
Q
What is a kWh
A
Killowatts per hour, 1000 watts in an hour
20
Q
How many joules in a kWh
A
3.6 x 10^6
21
Q
How many types of errors are there
A
2
22
Q
Types of errors
A
Random, systematic
23
Q
What do random errors affect
A
Precision
24
Q
How can you reduce a random error
A
Repeating and finding mean, using computers, use equipment with higher resolution
25
What causes systematic errors
Experimenter, instruments or method
26
What do systematic errors affect
Accuracy
27
How can you reduce a systematic error
Changing method or equipment, calibrate (measure known qty's to check equipment), read meniscus at eye level (curve of liquid), use controls, subtract background results (background radiation)
28
What is accuracy
How close your results are to true value
29
What is precision
Having similar values
30
What is repeatability
When the same person can get the same results each time with equipment and method
31
What is reproducibilty
When other people can the same results with different equipment or method
32
What is resolution
Scale of the instruments
33
Key features of a reading
Single judgement, absolute uncertainity is +/- half of smallest scale of division
34
Example of an instrument that gives readings
Thermometer
35
Key features of a measurement
Two judgements, chance for inaccuracies at either end of scale, absolute uncertainty is +/- smallest scale of division
36
Example of an instrument that gives measurements
Ruler, protractor
37
How to reduce fractional or percentage uncertainty
Measure larger quantities
38
Uncertainity of digital readings
Will either be told/known or can be assumed to be +/- the last significant digit - so resolution affects uncertainty
39
Uncertainity of a mean value
Half the range (largest - smallest value found)
40
Percentage uncertainty for a single reading
Abosolute uncertainity / measure value
41
Percentage uncertainty for a repeated reading
Half of range / mean value (range is largest-smallest value)
42
How to reduce uncertainty
Fix one end of ruler measuring a large space/instance and then dividing to find the required space/instance
43
How many significant figures to give the uncertainty to
Same as the significant figures of the data
44
Percentage uncertainty of gradient
|(LOBFm - WALOBFm)| / (LOBFm) *100
45
Percentage uncertainty of the Y-intercept
|(LOBFc - WALOBFc)| / (LOBFc) * 100
46
Absolute uncertainity of x when x = y + z
Absolute uncertainty of x = absolute uncertainty of y + absolute uncertainty of z
47
Percentage uncertainty of x when x = yz
Percentage uncertainty of x = percentage uncertainty of y + percentage uncertainty of z
48
Percentage uncertainty of x when x = y/z
Percentage uncertainty of x = percentage uncertainty of y + percentage uncertainty of z
49
Percentage uncertainty of x when x = y^a
Percentage uncertainty of x = (percentage uncertainty of y) * a
50
How to show uncertainties on a graph
Error bars - line of best fit must go through all
51
What is LOBF
Line of best fit
52
What is WALOBF
Worst acceptable line of best fit
53
How to find percentage uncertainty using max and min gradient
(max gradient - min gradient) / 2 * 100
54
Order of magnitude of wavelength of light
10^-7
55
Order of magnitude of mass of Earth
10^24
56
Order of magnitude of mass of sun
10^30
