Hall Effect a important topic of inorganic chemistry

1. HALL EFFECT

2. What is Hall Effect?
• THE PRODUCTION OF POTENTIAL DIFFERENCE ACROSS AN ELECTRICAL
CONDUCTOR WHEN A MAGNETIC FIELD IS APPLIED IN A DIRECTION
PERPENDICULAR TO THAT OF THE FLOW OF THE CURRENT.
• Hall Effect was introduced
by an American Physicist
Edwin H. Hall in the year
1879. It is based on the
measurement of the
electromagnetic field.

3. Principle:
• Lorentz Force
• For instance, if we place a magnetic bar nearby the conductor the magnetic field will
disturb the magnetic field of charge carriers. This force which distorts the direction of
charge carriers is known as Lorentz force.
F = qE + qv x B

4. Theory:
• Consider a thin conducting plate of length L and connect both ends of a plate with
a battery. Where one end is connected from the positive end of a battery to one end
of the plate and another end is connected from the negative end of a battery to
another end of the plate. Now we observe that currentl starts flowing from positive
end to the negative end of the plate.

5. If a perpendicular magnetic field is applied to the conductor. The path of the electrons
starts to curve. Due to this, the electrons will move to one end of the plate and holes
will move to another end of the plate. The moving charge creates a magnetic force.
This force interacts with external magnetic field and induces a force in one direction
called Lorentz force. The direction of this force is given by Flemings Left hand rule.

6. • The electrons stacking up in the
direction of force. The other side
there is a scarcity of charges. One
end is negative and other end is
positive creating the potential
difference. Here Hall voltage is
measured between two sides of
plates with a multimeter. This effect
is also known as the Hall Effect.
Where the current is directly
proportional to deflected electrons in
turn proportional to the potential
difference between both plates.
• Larger the current larger is the deflected electrons and hence we can observe
the high potential difference between the plates.

8. Formula:
• Hall Voltage is directly proportional to the electric current and applied magnetic field.
VH = I B / q n d
• Hall coefficient is given by,
RH = 1 / (nq)
VH - Hall voltage
I – Current flowing in Sensor
B – Magnetic Field Strength
q – Charge
n – charge carriers per unit volume
d – Thickness of the sensor
RH - Hall coefficient

9. Significance of Hall Effect:
• It can help us in determining the sign of the current carriers in metals and
semiconductors. Using the principles of the Hall effect, we can investigate
whether the conductivity of the material is due to the motion of electrons (it is
negative) or due to holes (it is positive).
• A straight graph plot between Hall voltage and current and also between Hall
voltage and magnetic field confirms their linear relationship. Using this point, we
can determine the current or magnetic field using the Hall effect, when others are
known.
• It helps in the determination of Hall Voltage, Hall current, Hall coefficient, hall
angle. It helps us in the measurements of the strength of magnetic field.

10. Applications Of Hall Effect:
1. Smartphones equipped with the Hall sensors.
Nowadays, many mobile phones are equipped with
leather cases, and the screen can be turned off
automatically when the leather cases are closed. This is
the function of the Hall sensor. If the handset is equipped
with the Hall sensor and has a built-in magnet inside the
leather cases, the screen can be turned off when the
leather cases are closed. When the flip cover or the phone
case is closed, the magnetic component is close to the hall
sensor. The hall sensor detects the signal, and shuts down
the screen or switches to the special window position.
Otherwise, the screen is turned on.

11. Charges flow in a thin metal strip (a key component in the smartphone Hall-effect
sensor) accumulate on the top and bottom surfaces due to the Lorentz force on charges,
induced by the externally magnetic field of a magnet mounted in the smartphone cover.
The strength of external magnetic field is proportional to the surface voltage, which can
be measured by a voltmeter.
Fig: Illustration of the principle of Hall-effect sensor and its application in
smartphone wake-up services by Jinlong Zhu, Renjie Zhau, Ni Zhao. 2020.
"Towards new form of particle sensing and manipulation and 3D imaging on a
smartphone for healthcare applications."

12. 2. Magnetometers
Magnetometers are extensively used in various applications like
geographical surveys, archeological surveys, metal detectors, space
explorations, etc. to detect the mineralization and geological structures.
In the oil and gas industry, these meters play an important role for a
directional drilling process. These meters are available based on the type
of applications like land, airborne, marine, and micro-fabricated atomic
magnetometers.

13. Magnetometers are used to measure the strength of the magnetic field and in some
cases direction of the field. These come under scientific instruments. A Hall effect
sensor that is attached to this device measures the flux density of the surrounded
magnetic field around it. Since the magnetic flux density is proportional to the
magnetic field strength so the output directly gives the intensity or strength of the
magnetic lines. Earth is surrounded by the lines of flux which vibrate at the different
frequencies depending on the locations. Any object or anomaly which distorts this
magnetic field is detected by a magnetometer.

14. 3. Proximity sensors:
Hall Effect Proximity Sensors are non-contact devices that
detect magnetic objects, offering high reliability and fast
response times in various applications.. The sensor is
made up of three primary components: a Hall Effect
sensor element, a signal processing circuit, and a
switching element.
The Hall Effect sensor element is a semiconductor device
that produces a Hall voltage when subjected to a magnetic
field. The signal processing circuit amplifies and filters
the Hall voltage to produce a usable output signal. The
switching element, typically a transistor or a digital
output, is then activated based on the output signal. When
the magnetic object comes within the sensor’s detection
range, the output signal changes, indicating the presence
of the object.

15. •Industrial Automation: These sensors are commonly used in automated systems for
detecting the position of machine parts, counting objects on a production line, or
measuring the speed of rotating equipment.
•Automotive Industry: Hall Effect sensors are essential components in various
automotive systems, such as anti-lock braking systems (ABS), throttle position sensors,
and crankshaft position sensors.
•Medical Devices: Hall Effect Proximity Sensors play a role in medical equipment,
including infusion pumps and prosthetic limb control systems.

16. 4. Spacecraft propulsions: Hall effect thrusters:
In spacecraft propulsion, a Hall-effect thruster (HET) is a type of ion thruster in which the
propellant is accelerated by an electric field. Hall-effect thrusters trap electrons in a magnetic
field and then use the electrons to ionize propellant, efficiently accelerate the ions to produce
thrust, and neutralize the ions in the plume. Hall-effect thrusters are sometimes referred to as Hall
thrusters or Hall-current thrusters. Hall thrusters are often regarded as a moderate specific
impulse (1,600 s) space propulsion technology. The Hall-effect thruster has benefited from
considerable theoretical and experimental research since the 1960s.

17. How Hall thrusters
work (and why we
can't simulate
them) - YouTube
Fig: Working of
HET by

18. Thank You