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Equations of the Quasi-static Field

Equations of the Quasi-static Field. Section 58. This requires: period of E >> electron response time. Otherwise E changes sign before macroscopic charge flow can build up. How does an E -field appear inside a conductor?.

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Equations of the Quasi-static Field

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  1. Equations of the Quasi-static Field Section 58

  2. This requires: period of E >> electron response time. Otherwise E changes sign before macroscopic charge flow can build up.

  3. How does an E-field appear inside a conductor? • Even though dh/dt is small, don’t discard it inside the conductor. • The external slowly-varying e-field does not penetrate, but the h-field does. • Thus, dh/dt is the only source for a macroscopic E-field inside.

  4. The field at a given point is determined by the j at the same point. • Requires: electron mean free path << characteristic length for changes in field. • Otherwise j at given point could be determined by E at distant points.

  5. Internal E arises from variations in B. To find B, we need H & constitutive relation.

  6. Quiz: If the external field is suddenly turned off, the field inside a conductor • Turns off at the same time • Decays exponentially in time with a multiple time constants • Decays exponentially in time with a single time constant • Decays linearly in time

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