Experimental Measurements and Uncertainties In A Level Physics experiments, it is crucial to understand the difference between precision and accuracy . Precisio...
In A Level Physics experiments, it is crucial to understand the difference between precision and accuracy. Precision refers to the consistency and reproducibility of measurements, while accuracy indicates how close a measured value is to the true or accepted value.
Experimental errors can be classified as either systematic or random:
To express the reliability of measurements, we calculate uncertainties. The absolute uncertainty represents the maximum expected deviation from the measured value, while the percentage uncertainty expresses this as a percentage of the measured value.
Measured length: 2.34 m ± 0.02 m
Absolute uncertainty = ±0.02 mPercentage uncertainty = (0.02 / 2.34) x 100% = ±0.85%
Quantities must be reported with an appropriate number of significant figures based on the uncertainty. When combining measurements through calculations, follow rules for determining the final significant digits.
Plotting data on graphs allows visual identification of trends and relationships. Apply lines of best fit to determine mathematical models describing the data. Check for proportionality and calculate gradients to find physical quantities.
The gradient of a velocity-time graph gives the acceleration. A proportional relationship between two quantities produces a straight line through the origin.
When designing experiments, identify independent, dependent, and control variables. Account for potential sources of error and minimize uncertainties. Analyze results critically, considering percent uncertainties when evaluating agreement with predicted values or models. Draw justified conclusions based on the experimental evidence.