China
Africa
Explore chapters and articles related to this topic
Basic Electromagnetic Theory
Published in Jianming Jin, in Magnetic Resonance Imaging, 2018
where ρs denotes the surface charge density, Js denotes the surface current density on the interface and, again, n̂ points from medium 2 to medium 1. Since a perfect conductor cannot sustain an electromagnetic field inside, the boundary conditions on a conducting surface become () Dn = ρs,Et = 0 () Bn = 0,n^ × H = Js.
Electrostatic Boundary Conditions
Published in Sivaji Chakravorti, Electric Field Analysis, 2017
A perfect conductor is defined as a material within which the charges are able to move freely. In electrostatics, it is considered that the charges have attained the equilibrium positions and are fixed in space. Theoretically, consider that the charges are initially distributed uniformly throughout the volume of a perfect conductor. Such distributed charges should be of same polarity within a conductor of one particular value of electric potential, because if there are charges of opposite polarity within the volume of the conductor, then such charges will immediately recombine with each other as they are free to move. Hence, the charges of same polarity that are present in the volume of the conductor will exert repulsive forces on each other. Because the charges are able to move without any hindrance, the charges will disperse in such a direction, so that the distance between the charges will increase. In the process all the charges will arrive at the surface of the conductor. But the conductor being surrounded by a dielectric, the charges are unable to move further and the charges will be fixed in space on the surface of the conductor. Consequently, any Gaussian surface within a perfect conductor will enclose zero charge and hence, electric field within a perfect conductor will be zero.
*
Published in Dikshitulu K. Kalluri, Principles of Electromagnetic Waves and Materials, 2017
Provided that the current density, the magnetic field, and the temperature are less than the threshold values, the resistivity drops to zero and the conductor may be treated as a perfect conductor. As we noted in the previous section, a DC magnified field HDC can exist in a conductor even though EDC = 0. However, in a perfect superconductor, it will be shown that HDC = 0. Thus, a perfect superconductor is not only a perfect conductor, but also a perfect diamagnet. The magnetic field in a specimen is expelled as the temperature is brought below the critical temperature Tc. This phenomenon is called the Meissner effect. We investigate the electromagnetic phenomena in a superconductor based on a macroscopic theory given by London.
Dynamo action between two rotating discs
Published in Geophysical & Astrophysical Fluid Dynamics, 2021
At an interface, the normal magnetic field and the tangential electric field must be continuous. Inside a perfect conductor the electric field must be zero else it would drive an infinite current. It follows that the tangential electric field on the discs must be zero, which from Ohm's law in the fluid translates to the tangential current must be zero, where is a unit vector in the z-direction. From the form of equations (7) and (10) this requires We note that the other tangential current component is automatically zero on the walls due to the nonslip condition and equation (9).