Mumbai university > FE > SEM 1 > Applied Physics 1

Marks: 5M

Year: May 2015

The Hall effect is the production of a voltage difference (the Hall voltage) across an electrical conductor, transverse to an electric current in the conductor and a magnetic field perpendicular to the current. It was discovered by Edwin Hall in 1879.

In solid-state physics, the electron mobility characterizes how quickly an electron can move through a metal or semiconductor, when pulled by an electric field. In semiconductors, there is an analogous quantity for holes, called hole mobility. The term carrier mobility refers in general to both electron and hole mobility in semiconductors.Electron and hole mobility are special cases of electrical mobility of charged particles in a fluid under an applied electric field.When an electric field E is applied across a piece of material, the electrons respond by moving with an average velocity called the drift velocity, $v_d$. Then the electron mobility μ is defined as

$$v_d = μE$$

Electron mobility is almost always specified in units of $cm^2/(V.s)$. This is different from the SI unit of mobility, $m^2/(V.s)$. They are related by $1m^2/(V.s) = 10^4cm^2/(V.s)$ . Significance of Hall effects are-

1) We can identify , whether the conductivity is due to electrons or holes.(for electrons hall effect is –ve, for holes it is +ve)

2) It is used to determine hall voltage, hall current, hall coefficient, hall angle,etc.

3) We can measure magnetic flux density.

4) These devices were capable of being employed in amplifier and oscillator circuits in radios and TVs, etc.