Definition of "magnetic field" [magnetic field]

• A condition found in the region around a magnet or an electric current, characterized by the existence of a detectable magnetic force at every point in the region and by the existence of magnetic poles. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The particle-beam could shut down a fusion drive for a couple of seconds by collapsing the magnetic field that squeezed the fuel together."
• "In addition, Hoxa Sound, which he had been told was unguarded, was defended by hydrophones, which picked up the sound of approaching ships; by seabed cables, which caused a galvanometer needle to flick when an electric current was induced by the magnetic field of a crossing vessel; and by mines, which could be detonated electrically from the shore."
• "Unlike regular MRIs, which use a powerful magnetic field to get images of your insides, fMRIs measure blood flow in the brain in an effort to determine which areas are activated by specific thoughts, reactions, or emotions."