Scribd
Upload
76 views2 pages

Measurement

The Hall effect occurs when a current-carrying conductor is placed perpendicular to a magnetic field, creating a potential difference across the conductor. This effect is small in conductors but measurable in semiconductors like germanium. When current flows through a semiconductor plate in a magnetic field, the field exerts a force on the charge carriers, pushing them to one side. This builds up electric fields that counteract the magnetic force until equilibrium is reached. The resulting Hall voltage is directly proportional to the current and magnetic field strength, and forms the basis for simple field-measuring instruments.

Uploaded by

chiranjeev
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOC, PDF, TXT or read online on Scribd
76 views2 pages

Measurement

The Hall effect occurs when a current-carrying conductor is placed perpendicular to a magnetic field, creating a potential difference across the conductor. This effect is small in conductors but measurable in semiconductors like germanium. When current flows through a semiconductor plate in a magnetic field, the field exerts a force on the charge carriers, pushing them to one side. This builds up electric fields that counteract the magnetic force until equilibrium is reached. The resulting Hall voltage is directly proportional to the current and magnetic field strength, and forms the basis for simple field-measuring instruments.

Uploaded by

chiranjeev
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOC, PDF, TXT or read online on Scribd
You are on page 1/ 2

Hall Effect Devices:

The Hall effect is named after the discoverer E. H Hall, who found that
when a dc current flows in a conductor which is perpendicular to a magnetic field, a
potential difference appears between the opposite edges of the conductor at right
angles to the current and to the magnetic field. This emf is very small in conductor
and is difficult to measure, but in some semi-conductors such as germanium, the emf
is sufficiently latge to be measured with a sensitive moving coil, instrument. This
phenomenon now forms the basis of some simple and elegant field-measuring
instruments.

The current is made up from electron and holes travelling in the opposite
direction. Current, i.e., the rate of flow of charge,

I= Nqvbt (1)

N : No of charge carriers per unit volume, each having q coulombs of charge


v: average velocity of the carriers in the direction of the current
b: breadth of the material
t: thickness of the material

There is a magnetic field or flux density B, crossing the thin plate, the
force on each chage,

FB = q v B (2)

FB will deflect the carriers to one side according to Flemming’s Left Hand
rule. Therefore, there is a tendency for charge to accumulate on one side of the
semiconductor, but the existence of this charge establishes an electric field which, in
turn, exercises an opposing force on the carriers (FE).

Ultimately an equilibrium is reached when the force due to magnetic filed


(FB) is equal to the force due to electric field.

1
Let, E: Electric field strength

The force on charge carriers, FE = qE (3)

Hence, qE +qVB = 0 (4)

v = - E/B (5)
NqEbt
Substituting v in (1), I = Nqvbt = -
B
IB
Or, E = - Nqbt
Since the electric field is uniform, the potential difference between opposite edges of
the semiconductor,

IB
V = - Eb = Nqt (6)
I
Nq
is called Hall Coefficient of the material.

For a given current, V ∞ B

You might also like