Detailed Notes: 1. Measurements and Their Errors: Paper 1: Physics A Level AQA

SI units are the fundamental units, they are made up of.

● Mass (m): kg (kilograms)

● Length (l): m (metres)

● Time (t): s (seconds)

● Amount of substance (n): mol (moles)

● Temperature (t): K (kelvin)

● Electric current (I): A (amperes)

Precision

Precise measurements are consistent, they fluctuate slightly about a mean value - this doesn’t indicate the value is accurate.

Repeatability

If the original experimenter can redo the experiment with the same equipment and method then get the same results it is repeatable.

Reproducibility

If the experiment is redone by a different person or with different techniques and equipment and the same results are found, it is reproducible.

Resolution

The smallest change in the quantity being measured that gives a recognisable change in reading.

Accuracy

A measurement close to the true value is accurate.

Uncertainty given as a fixed quantity e.g. 7±0.6 V.

Absolute Uncertainty

uncertainty as a fraction of the measurement e.g. 7 V± 3/35 V.

Fractional Uncertainty

uncertainty as a percentage of the measurement e.g. 7±8.6% V.

Percentage Uncertainty

Orders of magnitude

Powers of ten which describe the size of an object, and which can also be used to compare the sizes of objects.

E.g: The diameter of nuclei have an order of magnitude of around 10^-14 m.

100 m is two orders of magnitude greater than 1 m.

A skill physicists must use in order to approximate the values of physical quantities, in order to make comparisons, or to check if a value they’ve calculated is reasonable.

Estimation