BRAINCAKEMeasurements and Errors
Revision notes for Measurements and Errors in AQA Physics (7407). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.
- SI Base UnitsEvery physical quantity is a number multiplied by a unit.
- Derived UnitsA derived unit is made by combining SI base units, using the equation that defines the quantity.
- PrefixesPhysics deals with very large and very small values, so SI units are used with prefixes that multiply the unit by a power of ten.
- Converting UnitsCalculations must use consistent SI units, so you often need to convert values first.
- Random and Systematic ErrorsNo measurement is perfect.
- Precision, Repeatability and ReproducibilityPrecision describes how close repeated measurements of the same quantity are to each other.
- Resolution and AccuracyResolution is the smallest change in the quantity being measured that gives a perceptible change in the reading of an instrument.
- Absolute, Fractional and Percentage UncertaintyEvery measurement has an uncertainty: the interval within which the true value is expected to lie.
- Combining UncertaintiesWhen a result is calculated from several measured quantities, their uncertainties combine.
- Uncertainties on GraphsUncertainties in plotted data are shown on a graph with error bars.
- Uncertainty in a GradientWhen a gradient (or intercept) gives a physical quantity, you need its uncertainty.
- Estimation and Orders of MagnitudeThe order of magnitude of a quantity is its size given to the nearest power of ten.
On the specification
- 3.1.1 Use of SI units and their prefixes
- 3.1.2 Limitation of physical measurements
- 3.1.3 Estimation of physical quantities