Practical Skills

A-Level Physics OCR A, Module 1; source: physicsandmathstutor.com

Absolute Uncertainties

The interval that a value is said to lie within, with a given level of confidence

Accuracy

A measure of how close a measurement is to the true value

Analogue Apparatus

Measuring apparatuses that rely on the experimenter reading off a scale to determine the measurement

Anomalies

Data points that don't fit the pattern of data

What needs to be done during an experiment, before removing an anomalous result?

Determine why it has occurred

How can accuracy be improved in an experiment?

By taking repeat readings, removing anomalies, and calculating the mean

Control variables

Variables that must remain the same throughout an experiment, so as to not affect the results

Dependent Variables

The variable being measured in a experiment, and is dependent on the independent variable

On which axis should the dependent variable be plotted on?

y-axis

Digital Apparatus

Measuring apparatus that digitally measure and display a measurement

Fiducial Marker

A thin marker that is used to ensure readings are taken from the same place each time

How can measurements be taken more accurately?

Using a fiducial marker

Gradient

The change in the y-axis value over the change in the x-axis value between two points

How can the gradient of a curved line be found?

By drawing a tangent at a specific point

Independent variables

The variable that is changed by the experimenter in an experiment, which causes changes of the dependent variable

On which axis should the independent variable be plotted?

x-axis

Line of Best Fit

A line drawn on a graph to demonstrate the pattern in the plotted data points

Percentage Uncertainties

The uncertainty of a measurement, expressed as a percentage of the recorded value

Precision

A measure of how close measurement is to the mean value, to indicate the magnitude of random errors but not accuracy

Random Errors

Unpredictable variation between measurements that leads to a spread of values about the true value

How can random error be reduced?

By taking repeat measurements

Reliability

The ability for an experiment to be repeated using a different method, apparatus and experimenter, and still obtain the same results

Resolution

The smallest change in a quantity that causes a visible change in the reading that a measuring instrument records

SI Units

The International System of Units; the metric system

What is the SI unit for distance?

metres, m

What is the SI unit for mass?

kilograms, kg

What is the SI unit for time?

seconds, s

What is the SI unit for current?

amps, A

What is the SI unit for temperature?

kelvin, K

What is the SI unit for the amount of a substance?

moles, mol

Significant Figures

A measure of a measurement's resolution

Systematic Errors

Errors that cause all readings to differ from the true value by a fixed amount

How can systematic errors be avoided?

Using a different technique or apparatus

Parallax Errors

Errors that occur when an experimenter reads a measuring instrument wrong, and receives an incorrect measurement

Vernier Scales

The type of scale used on calipers and micrometers, that involve reading from a fixed scale and a moving scale to produce accurate measurements

Zero Errors

A form of systematic error that is caused when a measuring instrument doesn't read zero at a value of zero, causing all measurements being offset by a fixed amount