Final answer:
Magnetic survey methods map variations in the Earth's magnetic field to detect different materials, which is a technique also used in electromagnetic induction for metal detection. Visualization techniques include the use of iron filings or a compass to reveal the pattern and path of magnetic field lines.
Step-by-step explanation:
Magnetic survey methods work by mapping variations in the Earth's magnetic field. This is possible because different materials affect magnetic fields in various ways. For instance, you can map the magnetic field of a magnet by placing it under a sheet of paper and sprinkling iron filings on top. The iron filings align themselves with the magnetic field, allowing one to visualize the pattern of the field. Similarly, using a compass and drawing lines in the direction of the needle at various points around the magnet can show the path of the magnetic field line when these lines are connected.
Another significant application of these methods is in electromagnetic induction, which can detect metals. This is particularly important for finding buried landmines, in geophysical prospecting, and for security at airports. Fluctuations in the magnetic field induced by the presence of metallic objects allow for their detection, even when concealed.
To differentiate between a uniform electric and magnetic field, one could conduct measurements or observations on the effect of these fields on charged particles or magnetic materials, such as a compass, as electric fields and magnetic fields affect these differently.