Plot of electric flux lines

EMC Question of the Week: July 23, 2018

Gauss’ Law for magnetic flux, ∇∙B = 0, basically tells us that lines of magnetic flux

  1. have no beginning or end
  2. start and stop on electric charge
  3. are stronger in permeable materials
  4. are stronger in liquids

Answer

The correct answer is "a." In this equation, B is the magnetic flux density (a vector field). The divergence of a vector field is a measurement of how much the field strengthens or weakens at a given point. Unlike electric flux lines that grow stronger or weaker due to electric charge; lines of magnetic flux cannot grow stronger or weaker, because there is no magnetic equivalent to electric charge. Lines of magnetic flux always form complete loops. 

For a given magnetic field strength, H, lines of magnetic flux are stronger in permeable materials. This is described by the constitutive relationship, B = μH

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