EMC Question of the Week: December 4, 2017
Unlike electric currents, magnetic currents
- can flow on the surfaces of insulators
- always flow in closed loops
- produce magnetic fields
- don't exist in the real world
Answer
The best answer is "d". The concepts of a magnetic current and magnetic charge are useful for solving a wide variety of electromagnetic problems mathematically. By establishing a dual relationship between the electric field quantities and magnetic field quantities in Maxwell's equations, some complex problems can be reduced to simpler ones. For example, slots in a conducting plane can be modeled using equations normally applied to wire antennas.
Nevertheless, magnetic charges and currents have never been observed in the real world. The most likely explanation for this is that they don't exist, so "d" is the best answer. The first three choices are not good answers for the simple reason that they can be applied to electric currents. In the real world, small amounts of electric current can flow on the surface of insulators, due to moisture or other impurities on the surface. Electric currents always flow in closed loops, if we account for both conducted and displacement current. And, according to Ampere's Law, electric currents are always surrounded by magnetic fields. In mathematical simulations, magnetic currents are sometimes used as sources of electric fields.
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