OCR A LEVEL PHYSICS DEFINITIONS TOPIC 1 & 2

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 apparatus such as rulers, beakers and thermometers that rely on the experimenter reading off a scale to determine the measurement.

Anomalies

Data points that don’t fit the pattern of the data. You should determine why an anomalous result has occurred before removing it. Repeat readings help remove anomalies.

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 an experiment. It is dependent on the independent variable. The dependent variable should be plotted on the y-axis of a graph.

Digital Apparatus

Measuring apparatus such as ammeters, voltmeters and digital calipers that digitally measure and display a measurement.

Fiducial Marker

A thin marker, such as a splint, that is used to ensure readings are taken from the same place each time. They are used to improve the accuracy of measurements.

Gradient

The change in the y-axis value over the change in the x-axis value between two points. If the graph is curved, a tangent can be drawn to calculate the gradient at a specific point.

Independent Variables

The variable that is changed by the experimenter in an experiment. The independent variable should be plotted on the x-axis of a graph.

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 a measurement is to the mean value. It only gives an indication of the magnitude of random errors, not how close data is to the true value.

Prefixes

Added to the front of units to represent a power of ten change.

Random Errors

Unpredictable variation between measurements that leads to a spread of values about the true value. Random error can be reduced by taking repeat measurements.

Repeatable

The same experimenter can repeat a measurement using the same method and equipment and obtain the same value.

Reproducible

An experiment can be repeated by a different experimenter using a different method and different apparatus, 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.

Resolution of Forces

The splitting of a force into its horizontal and vertical components.

Scalar Quantities

A quantity that only has a magnitude, without an associated direction. Examples include speed, distance and temperature.

SI Units

The standard units used in equations. They are: metres, kilograms, seconds, amps, Kelvin and moles.

Significant Figures

A measure of a measurement’s resolution. All numbers except zero are counted as a significant figure. When zeros are found immediately after a decimal place, they too are counted.

Systematic Errors

Causes all readings to differ from the true value by a fixed amount. Systematic error cannot be corrected by repeat readings, instead a different technique or apparatus should be used.

Triangle of Forces

A method of finding the resultant force of two forces. The two forces are joined tip to tail and the result is then the vector that completes the triangle.

Vector Quantities

A quantity that has both a magnitude and an associated direction. Examples include velocity, displacement and acceleration.

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, caused when a measuring instrument doesn’t read zero at a value of zero. This results in all measurements being offset by a fixed amount.