1 - Measurements, errors and uncertainties

Question 1

What is a control variable?

Answer 1

Something that must be kept constant to prevent it affecting the dependent variable

Question 2

What is meant by the repeatability of results?

Answer 2

Similar results would be obtained from repeats of the same measurement from the same experimental set up

Question 3

What is meant by the reproducibility of results?

Answer 3

Similar results would be obtained from repeats by different people with different equipment

Question 4

How can you ensure a metre rule is held vertically?

Answer 4

Use a plumb line, set square or spirit level

Question 5

How do you avoid parallax error?

Answer 5

Ensure eye, object, and scale are all in line with each other OR ensure object and scale are directly adjacent to each other

Question 6

What is meant by the term random error?

Answer 6

Errors that cause the measurement to vary in unpredictable ways

Question 7

What is a systematic error?

Answer 7

An error that causes the measurements to differ from the true value by a consistent amount

Question 8

What is a zero error?

Answer 8

An error that occurs due to the measuring instrument reading a non-zero reading when the measured quantity is zero

Question 9

What is meant by the accuracy of a result?

Answer 9

How close a measurement is to the ‘true’ or accepted value

Question 10

What is meant by the precision of results?

Answer 10

How close repeated measurements are to eachother

Question 11

What is meant by the resolution of a measuring instrument?

Answer 11

The smallest change in quantity that can be measured

Question 12

What determines the resolution when using a multimeter?

Answer 12

The scale selected

Question 13

What is the resolution of a metre rule?

Answer 13

1mm

Question 14

What is the resolution of vernier callipers?

Answer 14

0.1mm

Question 15

What is the resolution of a micrometer?

Answer 15

0.01mm

Question 16

How do you find the absolute uncertainty from repeated readings?

Answer 16

± 1/2 the range of the repeats

Question 17

How do you estimate uncertainty when repeated results are identical?

Answer 17

± 1/2 the resolution of the instrument

Question 18

How do you calculate percentage uncertainty?

Answer 18

(Absolute uncertainty/Calculated or measured value) x100

Question 19

What do you do to the uncertainties when quantities are added or subtracted?

Answer 19

The absolute uncertainties are added together

Question 20

What do you do to the uncertainties when quantities are multiplied or divided?

Answer 20

The percentage uncertainties are added together

Question 21

What do you do to the uncertainties when a quantity is raised to a power?

Answer 21

The percentage uncertainty is multiplied by that power

Question 22

How do you find the uncertainty in a gradient?

Answer 22

±(gradient of line of best fit-gradient of line of worse fit)

Question 23

What is a line of worse fit?

Answer 23

The steepest or shallowest line that passes through the error bars

Question 24

What are error bars?

Answer 24

Lines to show the range of the absolute uncertainty of each data point on a graph

Question 25

What is a parallax error?

Answer 25

the apparent shift in an objects position as it is viewed from different angles

Question 26

What is the independent variable?

Answer 26

what we change or control in the experiment

Question 27

What is the dependent variable?

Answer 27

What we are testing and what will be measured in the experiment