Measurement observations made during an experiment need to be recorded in ways that are easy to follow.

Initially, results should be recorded in a table. The table of results should be planned before the experiment is performed.

The colums of the results table should include space for measurements that are taken and space for values which are going to be calculated from the measurements. Each column heading should include both the quantity and the unit. There should be a distinguishing mark (usually a forward slash ‘/’) to separate the quantity and the unit, for example, length / m, length (cm), L / mm etc.

Measurements taken in an experiment should be recorded to the same precision as the measuring instrument. For example, when using a ruler to measure lengthm measurements are made to the nearest millimeter, so a length of ten centimeters should be recorded as 10.0 cm. In timing experiments using a stopwatch, times can either be recorded to the nearest 0.01 s or rounded to the nearest 0.1 s.

Where calculated values are recorded in your results table, remember to label the column heading with both the quantitiy and the unit. For example, in an experiment to measure time, t, you may need to calcualte time squared t². In this case, the column should be labelled t²/s².

The calculated values should be recorded to the same number of significant figues as the raw data used to determine the calculated value.

For example, consider the diameter d of a wire. The calculated column may required d² to be determined.

As the values in table indicate, the change in the second significant figure affects the second sognificant figure in the calculated value.

Example table of results

In an experiment the potential difference V across a wire and the current I flowing through the wire are measured for different lengths L of the wire. The resistance of the wire is then calculated as shown in Table

At A level, you will need to understand how to calculate logarithms. For example, consider calculating the logarithm of L for the value of 22.2 cm from the Table.

In table, the number of significant figures (three) in the raw data (L) corresponds to the number of decimal places on the calculated logarithmic value. In general, logarithmic values should be given ti the same number of decimal paces as the least number of significant figures in the measured quantities.

Note the number before the decimal place in a logarithmic quantity is a place value. For example, in Table 22.2 cm can be written as 222 mm. In this case log (L/mm) = 2.346: only the number before the decimal place has changed.