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AQA A-level Physics > Measurements and their errors > Flashcards

Measurements and their errors Flashcards

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1
Q

What are SI units?

A

fundamental (base) units of physical quantites

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2
Q

What is the SI unit of mass?

A

kg (kilogram)

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3
Q

What is the SI unit for an amount of a substance? (mole)

A

mol

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4
Q

What is the SI unit for current?

A

A (amperes)

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5
Q

What is the SI unit for temperature?

A

K (kelvin)

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6
Q

What is the SI unit for length?

A

m (metres)

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7
Q

What is the SI unit for time?

A

s (seconds)

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8
Q

What is the standard form for T, Tera?

A

10^12

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9
Q

What is the standard form for G, Giga?

A

10^9

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10
Q

What is the standard form for M, Mega?

A

10^6

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11
Q

What is the standard form for k, kilo?

A

10^3

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12
Q

What is the standard form for c, centi?

A

10^-2

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13
Q

What is the standard form for m, milli?

A

10^-3

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14
Q

What is the standard form for µ, micro?

A

10^-6

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15
Q

What is the standard form for n, nano?

A

10^-9

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16
Q

What is the standard form for p, pico?

A

10^-12

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17
Q

What is the standard form for f, femto?

A

10^-15

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18
Q

Express 60T ohms in standard form

A

6 x 10^13

T= tera, 10^12

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19
Q

Write 0.000003m with a suitable prefix

A

3µm

20
Q

What is the actual value of 8M ohms?

A

8,000,000 ohms or 8 x 10^6 ohms

21
Q

What is something to remember about s.f.?

A

-the answers should be given with the same number of s.f. as the value with the least amount of s.f. used in the calculation
-in tables, all data needs to have the same s.f.

22
Q

What do we mean by accuracy?

A

how close a measurement is to the accepted (true) value

23
Q

What do we mean by precision?

A

how close measurements are to each other and the mean

24
Q

What is a random error?

A

these are errors in measurements which are unpredictable

25
Q

How can we reduce random errors? (3)

A

-repeat readings and find a mean
-use best-fit graph lines
-use computers/data loggers/cameras to reduce human errors e.g. reaction times

26
Q

What is a systematic error?

A

-errors which occur due to the apparatus or faults in the experimental method
-these cause all results to be too high or too low by the same amount each time

27
Q

How can we reduce systematic errors? (3)

A

-calibrate equipment
-use graph gradients to calculate values
-read measurements at eye level

28
Q

What is a zero error and how can we fix this?

A

-equipment that isn’t zeroed correctly
- take away starting reading from total when an object is measured

29
Q

What is a parallax error and how can we fix this?

A

-reading a scale at a different angle which can make the measurement seem off
-read the measurement at eye level

30
Q

What do we mean when an experiment is repeatable?

A

when the experiment is repeated with same method and equipment and achieves the same result

31
Q

What do we mean when an experiment is reproducible?

A

when the experiment is repeated using different equipment or method but still achieves the same result

32
Q

What is resolution?

A

the smallest increment on an apparatus

33
Q

What is uncertainty?

A

the bounds in which the accurate value can be expected to
lie

34
Q

How can we find the absolute uncertainty from a single judgment?

A

half the resolution

35
Q

How can we find the absolute uncertainty from two judgements?

A

2 x half the resolution

36
Q

How can we find the absolute uncertainty from repeat readings?

A

1/2 x range

37
Q

How can we find the absolute uncertainty from combined readings?

A

divide absolute uncertainty by no. of objects

38
Q

What s.f should the uncertainties be?

A

same as the data used

39
Q

How can we find fractional uncertanties?

A

absolute uncertainty of value/ value

40
Q

How can we find percentage uncertainties?

A

(absolute uncertainty of value/ value) x 100

41
Q

What do we do with the uncertainties when adding/subtracting data?

A

add absolute uncertanties

42
Q

What do we do with the uncertainties when multiplying/dividing data?

A

add percentage uncertanties

43
Q

What do we do with the uncertainties when we raise the data to a power

A

multiply percentage uncertainty by the power

44
Q

How can we show uncertainties on a graph?

A

use error bars

45
Q

How can we calculate the gradient percentage uncertainty from a graph?

A

-draw a steepest and shallowest line of worst fit, it must go through all the error bars.
-draw a ‘best’ line of best-fit which passes all the points close as possible

percentage uncertainty= (best gradient - worst gradient/ best gradient) x 100

46
Q

How can we calculate the y-intercept percentage uncertainty from a graph?

A

-draw a steepest and shallowest line of worst fit, it must go through all the error bars.
-draw a ‘best’ like of best-fit which passes all the points close as possible

percentage uncertainty= (best y-intercept - y-intercept/ best y-intercept) x 100

AQA A-level Physics (11 decks)

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