Pearson IGCSE Physics Practical 2: Measurement, Apparatus and Resolution

Reliable measurement begins with apparatus whose range and resolution suit the expected quantity.

In Pearson 4PH1 written practical questions, apparatus choice is part of the physics argument. A named instrument earns little if its connection, range, scale-reading method or limitation is wrong. The aim is to collect readings that can resolve the expected effect without overloading equipment or implying unsupported precision.

Measurement choices

• Check and record zero error before measuring.
• Read analogue scales perpendicular to the pointer or marker to reduce parallax.
• Use light gates or video when human reaction time would dominate short intervals.
• Measure multiple wavelengths, oscillations or thicknesses and divide to reduce percentage uncertainty.
• Select ammeter and voltmeter ranges that protect instruments while giving useful resolution.
• Repeat fluctuating readings and report a representative mean with sensible precision.

Range, resolution and uncertainty

The range is the span of values an instrument can measure. The resolution is the smallest scale division or display change it can distinguish. Neither term guarantees accuracy, which describes closeness to the accepted value. A high-resolution sensor can give consistently biased readings if it is badly calibrated.

Choose the smallest safe range that includes the expected reading. On a multirange ammeter, begin with a high range to protect the meter, then reduce the range for finer resolution if the current is safely below the limit. Never exceed a meter or sensor rating. A pilot measurement can establish the approximate value before the final range is selected.

For a single analogue reading, an uncertainty related to about half the smallest division is often a reasonable school-level estimate when the scale can be interpolated. For a change found from two readings, both endpoints contribute uncertainty. More important than memorising a rule is recognising when the uncertainty is large compared with the measured change. Measuring an extension of only $\pu{2 mm}$