1 - Measurements, errors and uncertainties Flashcards
What is a control variable?
Something that must be kept constant to prevent it affecting the dependent variable
What is meant by the repeatability of results?
Similar results would be obtained from repeats of the same measurement from the same experimental set up
What is meant by the reproducibility of results?
Similar results would be obtained from repeats by different people with different equipment
How can you ensure a metre rule is held vertically?
Use a plumb line, set square or spirit level
How do you avoid parallax error?
Ensure eye, object, and scale are all in line with each other OR ensure object and scale are directly adjacent to each other
What is meant by the term random error?
Errors that cause the measurement to vary in unpredictable ways
What is a systematic error?
An error that causes the measurements to differ from the true value by a consistent amount
What is a zero error?
An error that occurs due to the measuring instrument reading a non-zero reading when the measured quantity is zero
What is meant by the accuracy of a result?
How close a measurement is to the ‘true’ or accepted value
What is meant by the precision of results?
How close repeated measurements are to eachother
What is meant by the resolution of a measuring instrument?
The smallest change in quantity that can be measured
What determines the resolution when using a multimeter?
The scale selected
What is the resolution of a metre rule?
1mm
What is the resolution of vernier callipers?
0.1mm
What is the resolution of a micrometer?
0.01mm
How do you find the absolute uncertainty from repeated readings?
± 1/2 the range of the repeats
How do you estimate uncertainty when repeated results are identical?
± 1/2 the resolution of the instrument
How do you calculate percentage uncertainty?
(Absolute uncertainty/Calculated or measured value) x100
What do you do to the uncertainties when quantities are added or subtracted?
The absolute uncertainties are added together
What do you do to the uncertainties when quantities are multiplied or divided?
The percentage uncertainties are added together
What do you do to the uncertainties when a quantity is raised to a power?
The percentage uncertainty is multiplied by that power
How do you find the uncertainty in a gradient?
±(gradient of line of best fit-gradient of line of worse fit)
What is a line of worse fit?
The steepest or shallowest line that passes through the error bars
What are error bars?
Lines to show the range of the absolute uncertainty of each data point on a graph
What is a parallax error?
the apparent shift in an objects position as it is viewed from different angles
What is the independent variable?
what we change or control in the experiment
What is the dependent variable?
What we are testing and what will be measured in the experiment
