EMC Question of the Week: June 26, 2017
60 Hz electric field shielding is best accomplished using materials that have a,
- high conductivity
- high permeability
- high permittivity
- high atomic weight
Answer
The correct answer is "a". Materials with a high conductivity allow charge to flow readily. Charges will move on the surface of the material to locations required to make the electric field disappear within the material. If a shield encloses all of the field sources, the electric fields will be contained within the enclosure. A properly grounded and positioned shield can prevent electric field lines from reaching a particular place even when it does not enclose the space.
Permeability is a magnetic property of materials unrelated to electric field strength. Atomic weight (or relative atomic mass) is a property of chemical elements. There is no direct relationship between an element's atomic weight and the effectiveness of an electric field shield made from that element.
Materials with high electric permittivity can be used to redirect electric field lines to some extent, but they do not make good electric field shields.
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