A Level Physics Practice Exam 2025 - Free A Level Physics Practice Questions and Study Guide

A zero error occurs when a measuring instrument gives a reading when it should read zero, indicating that the instrument is not correctly calibrated to the true zero point of measurement. When the instrument starts measuring from a non-zero value, this directly shows that there is a systematic error present right from the beginning of the measurement process, leading to inaccuracies in subsequent measurements.

For example, if a ruler shows that it measures 1 cm when no object is actually present, this means all subsequent measurements will be consistently offset by that 1 cm, leading to zero error. Thus, identifying that the instrument does not start from an expected zero point is crucial in recognizing zero error.

The other options, while related to measurement inaccuracies, do not specifically indicate zero error. Inconsistent readings may suggest random errors or issues with the instrument itself, fluctuations in ambient conditions could affect the measurements but wouldn't point specifically to a zero error, and failure to calibrate to a reference value indicates general inaccuracy rather than a direct zero error unless it highlights a non-zero starting point.