Measurements and their errors

Question 1

What are SI units?

Answer 1

fundamental (base) units of physical quantites

Question 2

What is the SI unit of mass?

Answer 2

kg (kilogram)

Question 3

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

Answer 3

mol

Question 4

What is the SI unit for current?

Answer 4

A (amperes)

Question 5

What is the SI unit for temperature?

Answer 5

K (kelvin)

Question 6

What is the SI unit for length?

Answer 6

m (metres)

Question 7

What is the SI unit for time?

Answer 7

s (seconds)

Question 8

What is the standard form for T, Tera?

Answer 8

10^12

Question 9

What is the standard form for G, Giga?

Answer 9

10^9

Question 10

What is the standard form for M, Mega?

Answer 10

10^6

Question 11

What is the standard form for k, kilo?

Answer 11

10^3

Question 12

What is the standard form for c, centi?

Answer 12

10^-2

Question 13

What is the standard form for m, milli?

Answer 13

10^-3

Question 14

What is the standard form for µ, micro?

Answer 14

10^-6

Question 15

What is the standard form for n, nano?

Answer 15

10^-9

Question 16

What is the standard form for p, pico?

Answer 16

10^-12

Question 17

What is the standard form for f, femto?

Answer 17

10^-15

Question 18

Express 60T ohms in standard form

Answer 18

6 x 10^13

T= tera, 10^12

Question 19

Write 0.000003m with a suitable prefix

Answer 19

3µm

Question 20

What is the actual value of 8M ohms?

Answer 20

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

Question 21

What is something to remember about s.f.?

Answer 21

-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.

Question 22

What do we mean by accuracy?

Answer 22

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

Question 23

What do we mean by precision?

Answer 23

how close measurements are to each other and the mean

Question 24

What is a random error?

Answer 24

these are errors in measurements which are unpredictable

Question 25

How can we reduce random errors? (3)

Answer 25

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

Question 26

What is a systematic error?

Answer 26

-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

Question 27

How can we reduce systematic errors? (3)

Answer 27

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

Question 28

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

Answer 28

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

Question 29

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

Answer 29

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

Question 30

What do we mean when an experiment is repeatable?

Answer 30

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

Question 31

What do we mean when an experiment is reproducible?

Answer 31

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

Question 32

What is resolution?

Answer 32

the smallest increment on an apparatus

Question 33

What is uncertainty?

Answer 33

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

Question 34

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

Answer 34

half the resolution

Question 35

How can we find the absolute uncertainty from two judgements?

Answer 35

2 x half the resolution

Question 36

How can we find the absolute uncertainty from repeat readings?

Answer 36

1/2 x range

Question 37

How can we find the absolute uncertainty from combined readings?

Answer 37

divide absolute uncertainty by no. of objects

Question 38

What s.f should the uncertainties be?

Answer 38

same as the data used

Question 39

How can we find fractional uncertanties?

Answer 39

absolute uncertainty of value/ value

Question 40

How can we find percentage uncertainties?

Answer 40

(absolute uncertainty of value/ value) x 100

Question 41

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

Answer 41

add absolute uncertanties

Question 42

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

Answer 42

add percentage uncertanties

Question 43

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

Answer 43

multiply percentage uncertainty by the power

Question 44

How can we show uncertainties on a graph?

Answer 44

use error bars

Question 45

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

Answer 45

-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

Question 46

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

Answer 46

-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