Motional Emf Research Articles

Simplified theory of nonuniform electrical conduction for an open cycle MHD generator with shaped magnetic induction

Simplified formulae were derived for the approximate evaluation of electrical performances of an MHD generator with nonuniform equilibrium plasma. In order to clarify the effectiveness of the propperly shaped nonuniform magnetic induction of type B ∞ n e , the transverse component B y was included in the formulation of the theory. It was shown that the terminal characteristics of the generator, such as the internal resistance, the motional emf, the current and the output power could be improved significantly under the shaped B z ∞ n e type of applied magnetic induction for wide ranges of electrodeand insulator wall temperatures, channel sizes and averaged intensities of the magnetic induction.

Motional EMF and animal navigation (teaching problem)

An elementary analysis of the aeroplane problem is given, and then, as an illustrative example, the possibilities of this mechanism for animal navigation are briefly considered. The problem is that of a metal aeroplane of total wingspan L moving in level flight through the vertical component B of the geomagnetic field with a steady ground speed U. The potential difference which is generated between the wing tips is to be calculated.

Phase-matched electromagnetic generation and detection of surface elastic waves on nonconducting solids

We have generated and detected surface elastic waves at a fundamental frequency of 15.5 MHz on high-resistivity silicon. The generation process involved the Lorentz forces exerted by a static magnetic field on the current-carrying elements of an evaporated aluminum meander line whose spatial periodicity matched that of the surface waves. The detection process involved the motional emf induced by the magnetic field in the vibrating elements of the receiver meander line. The generation-detection signal amplitude shows a B2 dependence and is a maximum when the magnetic field is parallel to the direction of propagation.

Io as an emitter of 100-kev electrons

If the surface conductivity of Jupiter's satellite Io is greater than 5 × 10−11 Ω−1 cm−1 and if the height-integrated Pederson conductivity of the Jovian ionosphere is greater than 0.6 mho, then it is likely that significant Debye and photoelectron sheaths form around Io. When the current balance condition between emitted photoelectrons and collected ambient electrons is used, the potential across the sheath can approach the 670-kV motional emf developed as Io moves through the Jovian magnetic field. The characteristic sheath thickness is estimated to be 50 km. As a result of the Debye sheath, photoelectrons emitted at the surface of Io can be accelerated to several hundred keV along the magnetic field lines and precipitate into the Jovian atmosphere with a flux of 105 el m−2 s−1 eV−1 averaged over the Io flux tube. This electron beam may carry in excess of 1010 W and may cause the decametric emissions. Also, 1024 el s−1 may be trapped on the field lines associated with Io. These electrons may cause the decimetric synchrotron emission. Variations of the electron spectra are considered as a function of Io’s orbital position accounting for the tilted dipole field.