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Definition
The Hall effect is the production of a
voltage difference (the Hall voltage)
across a current carrying conductor (in
presence of magnetic field),
perpendicular to both current and the
magnetic field.
Discovery
The Hall effect was discovered in 1879
by Edwin Herbert Hall while working on
his doctoral degree at the Johns
Hopkins University in Baltimore,
Maryland, USA.
Theory
• A static magnetic field has no effect on
a charged particle unless it is moving.
• When charges flow, a mutually
perpendicular force (Lorentz force) is
induced on the charge.
• Now electrons and holes are separated
by opposite force.
Theory
• This produces a electric field which
depends upon cross product of magnetic
intensity [H] and current density [J]
Eh=R(JxH)
• R is called Hall Coefficient
• Consider a Semiconductor bar along Xaxis, Magnetic field along Z-axis. Thus
Eh will be along Y-axis.
Theory
• Thus R=Vh/aJH=Vhb/IH
• Vh is Hall Voltage and I is Jab
Setup
Electromagnet
Digital hall
effect setup
Hall Probe
Gaussmeter
Working
1. Conductor is kept
in a magnetic
field.
2. Current is passed
through it.
3. We get a reading
in voltmeter kept
perpendicular to
the conductor.
•
After setup the
Hall Voltage is
measured as a
function of –
1. Current keeping
magnetic field
constant.
2. Magnetic field
keeping current
constant.
Hall Voltage
Recording Observation
Current
Conclusions
1. Hall Coefficient can be determined using
Rh=Vhb/IH
2. Hall effect can be used to determine the signs of
current carrier in metals and semiconductor.
3. A straight graph between Hall voltage & Current
and between Hall voltage & Magnetic field
confirms their linear relationship. This point has
important meaning as hall effect can be
effectively used to determine current or magnetic
field, when other is known.
Precautions
1. Hall Voltage should be measured very
carefully and accurately.
2. Distance between pole pieces of
Electromagnet should not be changed
during the whole experiment.
3. Current passing through
semiconductor slab should be strictly
within permissible limit.
Applications
Hall effect devices produce a very low
signal level and thus require
amplification. In early 20th century
vacuum tube amplifiers were expensive
and unreliable. But with the
development of the low cost integrated
circuit the Hall effect sensor became
suitable for mass application.
Current Sensor
• When electrons flow through
a conductor, a magnetic field
is produced.
• Thus, it is possible to create a
non-contacting current
sensor. This has several
advantages:
1. No additional resistance (a
shunt) need be inserted in
the primary circuit.
2. Also, the voltage present
on the line to be sensed is
not transmitted to the
sensor, which enhances
the safety of measuring
equipment.
Hall effect current sensor with
internal integrated circuit amplifier.
Electric Motor Control
Some types of brushless
DC electric motors use Hall
effect sensors to detect the
position of the rotor and
feed that information to the
motor controller. This
allows for more precise
motor control.
Magnetometer
• Smart phones like iPhone
3GS are equipped with
magnetic compass.
• These compass measure
Earth‘s magnetic field using
3-axis magnetometer.
• These magnetometer are
sensors based on Hall Effect.
• These sensors produce a
voltage proportional to the
applied magnetic field and
also sense polarity.
And there are many more
applications of hall effect…