Aristotle On Exams

Discover how to think like a designer

Emergence in a with current j density, N, in a magnetic field, electric field of Ekh, perpendicular N and j is called as effect of the Hall. Thus the of the electric field called still by the Hall field is equal:

where  a corner between vectors of N and J ( <180 °). When Hj, size of a field of Hall Ekh is maximum: Ex = RHj. R called by Hall's coefficient is the main characteristic of effect of Hall. The effect is opened by Edwin Herbert Hall in 1879 in thin of gold. For Hall's supervision of effect along rectangular plates from substances, l which length is more than width of b and thickness of d, current :

Sometimes at the description of the Hall of effect enter a corner of the Hall of  between current of j and the direction of a total field E: tg = Ex/E=, where  — the cyclotron frequency of of a charge. In weak fields ( <

Let's consider one of opportunities of strengthening of effect on the example of two Hall elements one of which (I) is the Hall field generator, and the second (II) — loading. The scheme of connections of Hall elements I and II is shown in drawing.

By means of the Hall of EMF of the sensor it is possible to measure any physical quantity which is unambiguously connected with a magnetic field; in particular it is possible to change the current as round the conductor with current the magnetic field which can be measured is formed. On the basis of the Hall of EMF of the sensor ampermeters on currents to 100 kA are created. Except that Hall of EMF sensors are used in measuring instruments of linear and angular movements, and also in measuring instruments of a gradient of a magnetic field, magnetic flux and power of electrical machines, in contactless converters of a direct current in variable, and, at last, in the reproducing heads of systems of a sound recording.

The important characteristic of substance is mobility in is mute current carriers. The average speed acquired by carriers at intensity of an field, equal unit is called as mobility of carriers of current. If in the field of intensity E get u speed that mobility of their u0 is equal:

Mobility can be connected with  and concentration of carriers n. For this purpose we will divide j=neu ratio into intensity of a field E. Having taken into account that j relation to E gives , and u relation to E - mobility, we will receive:

Tolmen and Stewart's experience in which the impulse of current of j connected with inertia of free electrons was observed is known. At inertial division of charges in the conductor there is an electric field intensity of E. If to place such conductor in a magnetic field of B, it is necessary to expect emergence of the EMF similar to effect of the Hall caused by action of Lorentz force on inertial electrons.

The new physical effect caused by action of Lorentz force on electrons of the semiconductor is predicted, moving is accelerated. Expression for a field of the Hall is received and estimates of Hall tension for real two-dimensional heterostructure are executed. The analysis of the possible scheme of strengthening of a Hall field on the example of two Hall elements, one of which — tension generator, and the second — loading is made.