Final answer:
The effectiveness of a compass is influenced by the strength of nearby magnetic fields. Strong magnetic fields, significantly stronger than the Earth's, can disrupt compass readings.
Step-by-step explanation:
The range within which a field can affect a compass depends largely on the strength of the magnetic field. Small compasses, like those used in experiments, do not disturb the magnetic field they are testing. However, strong magnetic fields, like those created by unpaired wires carrying significant electric current, can severely disrupt the use of a compass. For instance, if a field is about ten times stronger than Earth's magnetic field, it can affect compass readings significantly. Surveyors working near strong electromagnetic sources, such as high-voltage power lines, might encounter such interference. In a practical scenario, surveyors must consider the impact of these fields and use tools or methods to correct for any compass deviation.