Electricity and magnetism

Barnett effect , the magnetisation of ferromagnets when they are rotated in the absence of a magnetic field; discovered in 1909 by the American physicist S.

Moving striations , dark and light layers (strata) that move continuously along the positive column of a glow discharge or an arc discharge.

Electrodeless discharge , one of the kinds of high-frequency discharge (or of pulsed discharge) in which the discharge gap is completely isolated from electrodes, and the discharge current may be either a displacement cu…

in a plasma, see Landau damping.

Gapless semiconductors, semiconductors with a forbidden-band width Ε g = 0.

Beta-spectrometer , an instrument for measuring the energy distribution (the spectrum) of the electrons and positrons emitted in β-decay, and also of conversion electrons and of the electrons produced when gamma, X-ray a…

Betatron - a cyclic electron accelerator in which the acceleration is produced by the vortex electric field induced by an alternating magnetic field enclosed by the circular orbit of the particles. ( see Accelerators ).

Biot-Savart law determines the magnetic field strength produced by an electric current.

see Interaction in physics.

Bolometer , ( from the Greek bole — a throw; a ray, and metreo — I measure), a thermal non-selective detector of optical radiation, based on the change in the electrical resistance of a heat-sensitive element when it is …

see Magneton.

Bohr–Van Leeuwen theorem - a theorem of classical statistical physics, according to which the magnetisation of a system of electrons in a constant external magnetic field under conditions of statistical equilibrium is eq…

Brewster's law, the relation between the refractive index n of a dielectric and the angle of incidence φ of natural (unpolarised) light on it at which the light reflected from the surface of the dielectric is completely …

The gimlet rule gives the direction of the magnetic field produced by an electric current: if a gimlet with a right-hand thread is screwed in along the direction of the current I (Fig.), the direction in which its handle…

The SI unit of the reactive power of an alternating (sinusoidal) electric current. 1 var is equal to the reactive power at root-mean-square values of the electric voltage of 1 V and of the current of 1 A and at sin φ=1 (…

Weber , (Wb), the SI unit of magnetic flux and of flux linkage.

Galvanometer, an electrical measuring instrument of high sensitivity for measuring small currents, voltages and quantities of electricity (see Ballistic galvanometer ).

Gauss's theorem , the fundamental theorem of electrostatics, which relates the flux of the electric field strength E through a closed surface S to the magnitude of the charge q contained inside that surface.

Dynamo effect (hydromagnetic dynamo), the self-excitation of magnetic fields by the motion of a conducting liquid or a gaseous plasma.

Dipole moment , electric, a quantity characterising the electrical properties of a system of charged particles.