Hall Effect

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Hall Effect

• Presented By

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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.

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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.

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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.

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Theory

• This produces a electric field which depends upon
  cross product of magnetic intensity H and
  current density J
• EhR(JxH)
• R is called Hall Coefficient
• Consider a Semiconductor bar along X-axis,
  Magnetic field along Z-axis. Thus Eh will be
  along Y-axis.

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Theory

• Thus RVh/aJHVhb/IH
• Vh is Hall Voltage and I is Jab

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Setup
Electromagnet
Gaussmeter
Digital hall effect setup
Hall Probe
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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.

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Recording Observation

• After setup the Hall Voltage is measured as a
  function of
• Current keeping magnetic field constant.
• Magnetic field keeping current constant.

Hall Voltage
Current
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Conclusions

1. Hall Coefficient can be determined using
   RhVhb/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.

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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.

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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.

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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
• No additional resistance (a shunt) need be
  inserted in the primary circuit.
• 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.
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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.

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Magnetometer

• Smart phones like iPhone 3GS are equipped with
  magnetic compass.
• These compass measure Earths 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.

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And there are many more applications of hall
effect