Seebeck Effect

As shown in the figure, when two different conductors a and b are connected at both ends to form a closed circuit, if the two joints A and B have different temperatures, there will be current in the circuit. This current is called thermoelectric current , This loop constitutes the so-called thermocouple, the electromotive force that produces the current is called thermoelectromotive force, and its value is generally only related to the temperature of the two joints. This effect was discovered by Seebeck in 1821, so it is called the Seebeck effect, and the thermoelectromotive force is also called the Seebeck electromotive force.

Thermal conductivity of semiconductors

When the temperature of a certain part of the crystal rises, the heat energy will be conducted from the high temperature part of the crystal to the low temperature part, so that the temperature of the whole crystal tends to be uniform. Take a one-dimensional case as an example, imagine a small area ds in the crystal, and the temperature gradient of dT / dx along the x direction, then the heat Q through the area ds and the area ds, the temperature gradient dT / dx and time in dt time dt is proportional to

The minus sign indicates that the heat flows from high temperature to low temperature; k is called the thermal conductivity of the crystal, and the unit is:W/（m▪K）。

Hall Effect

Put a current-carrying semiconductor in a uniform magnetic field, set the electric field along the X direction and the electric field strength as Ex; the direction of the magnetic field is perpendicular to the electric field, along the z direction, and the magnetic field induction strength is Bz. The -y direction will produce a transverse electric field Ey, this phenomenon is called the Hall effect. Hall electric field Ey is proportional to current density Jx and magnetic field induction intensity Bz, namely

E_y=R_HJ_xB_z

The proportional coefficient RH is called the Hall coefficient, namely

(Source: Seventh Edition of "Semiconductor Physics" Electronic Industry Press)

Magnetic Field

(International Electrotechnical Commission IEC's definition) The components of the electromagnetic field are characterized by magnetic field strength H and magnetic flux density B. (Chinese national standard definition) The magnetic field is a kind of field whose characteristics can be determined by the force of the charged particles moving in the field. This force comes from the movement of the particle and the charge it carries.

Hysteresis Loop

 Measurement of uniformity of uniformity zone 

Measuring the uniformity of the uniform area: Make the power output to a certain value and wait for it to stabilize, measure the central magnetic field of the coil, and move the field meter smoothly in the uniform area to ensure that the probe does not tilt and rotate, and record the value of the magnetic field at each point in the uniform area. If the central magnetic field value is H0 and the magnetic field value of another point in the uniform zone is H1, then the magnetic field deviation at this point is ΔH=H1-H0, and the uniformity of the magnetic field at this point is ΔH/H0;

Common conversion unit of magnetic quantity