> [[Environmental Conditions MOC]] • [[Magnetic Fields]] ## why do we care? magnetic fields make wobbly images ![[magnetic fields make wobbly images]] ## Source area effects AC magnetic fields decrease in intensity as function of distance (d) from the source. The rate of decrease can vary depending on the source. - Magnetic fields from **motors, transformers, etc.** decrease quickly (**1/d3**) - while circuits in a typical **multi-conductor circuit** decay slower (**1/d2**). - Magnetic fields from **“stray” current** on water pipes, building steel, etc. tend to decay much slower (**1/d**). ## sources of magnetic fields - [[Underground magnetic anomalies]] - [[magnetic fields from household appliances|household appliances]] - [[magnetic fields from a conductor|power conductors]] - [[magnetic fields from power distribution boards|power distribution boards]] - [[magnetic fields from ground current leakage|Ground current leakage]] - [[Diverted Neutrals]] - [[magnetic fields from lighting|Lighting]] - [[magnetic fields from elevators|Elevators]] ## Survey techniques and examples - [[Detecting magnetic anomalies with multiple magnetometers]] - [[Literature Building Magnetic Field Survey]]