Alternating magnetic flux

An alternating voltage applied to the primary winding establishes an alternating magnetic flux in the core. 

The rotor is placed in the center of the stator. An A.C. (alternating current) power supply is applied (voltage) to the stator coils. A magnetic flux is produced in the small space between the rotor and stator... 

Based on equation (8) one can obtain alternative methods for the calculation of the electronic contribution to the g tensor by differentiating expressions for the electronic energy in the presence of an ejrternal magnetic flux density B and the coupling with the rotational motion Using equation (6) the... 

Figure 2 Experimental arrangement for measurements of the Fe nuclear resonance at the Advanced Photon Source (APS). In the standard fill pattern, electron bunches with a duration of 100 ps are separated by 153 ns. X-ray pulses are generated when alternating magnetic fields in the undulator accelerate these electron bunches. The spectral bandwidth of the X-rays is reduced to 1 eV by the heat-load monochromator and to 1 meV by the high-resolution monochromator. At the sample, the flux of the beam is about 10 photons/s. APD indicates the avalanche photodiode used to detect emitted X-rays. The lower right inset illustrates that counting is enabled only for times weU-separated from the X-ray pulse, so that only delayed photon emission resulting from decay of the nuclear excited state contributes to the experimental signal...

The principle of eddy current testing is based on the interaction between an electrical current induced in a material and the structure of the material tested. A primary magnetic field is generated in the vicinity of a coil excited by an alternating current (Fig. 7). The magnetic flux density 4) associated with the primary magnetic field is proportional to the magnitude I of the electric current within the coil and to the number N of turns in the coil ... 

A further enhancement is provided by alternative detection methods. Pines and co-workers " " have coupled the use of HP xenon with a SQUID, which provides very high-sensitivity detection of magnetic fluxes at low resonance frequencies. The authors showed that the use of optically pumped xenon and a high-Tc SQUID device could be coupled to allow the detection of laser-polarized xenon gas at only 27 kHz, corresponding to a magnetic field of 2.3 mT. MRI of xenon adsorbed on a piece of silica aerogel was also shown using this approach (see Fig. 27). " SQUID... 

When an alternating magnetic field is applied to a ferromagnetic material, it induces an electromotive force, denoted emf, in volts, which generates an eddy current. The Joule s heating, that is, the power released per unit mass of magnetic material, denoted P, due to the eddy current is termed eddy-current losses also known as Foucault-current losses and it is expressed in W/kg. For a low frequency, /, expressed in Hz, the flux penetration into the material is complete and proportional to / and to the reciprocal of the electrical resistivity. 

Armature The member of a rotating electric machine in which an alternating voltage is generated by virtue of relative motion with respect to a magnetic-flux field. 

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