Search results for "magnetic potential"

Recovery of time-dependent coefficients from boundary data for hyperbolic equations

2019

We study uniqueness of the recovery of a time-dependent magnetic vector-valued potential and an electric scalar-valued potential on a Riemannian manifold from the knowledge of the Dirichlet to Neumann map of a hyperbolic equation. The Cauchy data is observed on time-like parts of the space-time boundary and uniqueness is proved up to the natural gauge for the problem. The proof is based on Gaussian beams and inversion of the light ray transform on Lorentzian manifolds under the assumptions that the Lorentzian manifold is a product of a Riemannian manifold with a time interval and that the geodesic ray transform is invertible on the Riemannian manifold.

Imaging magnetic scalar potentials by laser-induced fluorescence from bright and dark atoms

2014

We present a spectroscopic method for mapping two-dimensional distributions of magnetic field strengths (magnetic scalar potential lines) using charge-coupled device (CCD) recordings of the fluorescence patterns emitted by spin-polarized Cs vapour in a buffer gas exposed to inhomogeneous magnetic fields. The method relies on the position-selective destruction of spin polarization by magnetic resonances induced by multi-component oscillating magnetic fields, such that magnetic potential lines can be directly detected by the CCD camera. We also present a generic algebraic model allowing for the calculation of the fluorescence patterns and find excellent agreement with the experimental observa…

Magnetic potential of transformer window

1996

We describe how to calculate the magnetic potential in the window of an ideal transformer. The knowledge of this potential is a starting point for the determination of some other quantities of practical importance (such as leakage field, overheating of windings, circular currents, additional losses, short circuit forces in windings, etc.).

Analysis of the static and dynamic behaviour of a magnetic liquid seal

1985

A rotating shaft seal, using ferrofluid between biconical truncated magnetic poles, is analysed both in static and dynamic conditions. After solving Laplace's equation and allowing an approximate expression for the magnetic potential, the magnetic forces acting on the working fluid are obtained. It is thus possible to determine the baric field existing in static conditions and the highest tolerable pressure jump. In the case of dynamic working the flow is schematized by two interior regions, where the azimuthal velocity prevails, and four boundary layers on the walls, where meridional transport of fluid takes place. Assuming laminar motion, by means of a perturbation procedure it is possibl…

An educational path for the magnetic vector potential and its physical implications

2013

We present an educational path for the magnetic vector potential A aimed at undergraduate students and pre-service physics teachers. Starting from the generalized Ampere–Laplace law, in the framework of a slowly varying time-dependent field approximation, the magnetic vector potential is written in terms of its empirical references, i.e. the conduction currents. Therefore, once the currents are known, our approach allows for a clear and univocal physical determination of A, overcoming the mathematical indeterminacy due to the gauge transformations. We have no need to fix a gauge, since for slowly varying time-dependent electric and magnetic fields, the ‘natural’ gauge for A is the Coulomb o…

Stability analysis of an electromagnetically levitated sphere

2006

We present a combined numerical and analytical approach to analyze the static and dynamic stabilities of an electromagnetically levitated spherical body depending on the ac frequency and the configuration of a three-dimensional (3D) coil made of thin winding which is modeled by linear current filaments. First, we calculate numerically the magnetic vector potential in grid points on the surface of the sphere and then use Legendre and fast Fourier transforms to find the expansion of the magnetic field in terms of spherical harmonics. Second, we employ a previously developed gauge transformation to solve analytically the 3D electromagnetic problem in terms of the numerically obtained expansion…

Corrigendum: An educational path for the magnetic vector potential and its physical implications

2014

Reply to Comment on ‘An educational path for the magnetic vector potential and its physical implications’

2014

In this reply we respond to the comment made by Heras on our paper (Barbieri et al 2013 Eur. J. Phys. 34 1209), in which we presented an educational path on the magnetic vector potential A, aimed at undergraduate students and pre-service physics teachers.

Resolvent estimates for the magnetic Schrödinger operator in dimensions ≥2

2020

It is well known that the resolvent of the free Schrödinger operator on weighted L2 spaces has norm decaying like λ−12 at energy λ . There are several works proving analogous high frequency estimates for magnetic Schrödinger operators, with large long or short range potentials, in dimensions n≥3 . We prove that the same estimates remain valid in all dimensions n≥2 . peerReviewed

An equivalent single-layer model for magnetoelectroelastic multilayered plate dynamics

2012

Abstract An equivalent single-layer model for the dynamic analysis of magnetoelectroelastic laminated plates is presented. The electric and magnetic fields are assumed to be quasi-static and the first-order shear deformation theory is used. The formulation of the model provides for a preliminary fulfillment of the electro-magnetic governing equations, which allows to determine the electric and magnetic potential as functions of the mechanical variables. Then, by using this result, the equations of motion are written leading to the problem governing equations. They involve the same terms of the elastic dynamic problem weighted by effective stiffness coefficients, which take the magneto-elect…