 Namaste. Myself, Dr. Mrs. Preeti Sunil Joshi, working as assistant professor in Valchand Institute of Technology, Solapur. In this session, we are going to study applications of Hall effect. Learning outcomes are, by the end of this session, students will be able to state applications of Hall effect in various fields. The contents include applications of Hall effect. In 1879, EH Hall discovered that, if a metal or semiconductor that is carrying current i, if it is placed in a transverse magnetic field B, then a potential difference VH is produced in a direction normal to both the magnetic field and current directions. This is known as Hall effect. This effect established that it is negatively charged particles that carry current in metals. The importance of Hall effect in the field of semiconductors is that, it helps to determine the type of semiconductor, sign of majority charge carriers, majority of charge carrier concentration, mobility of majority charge carriers, mean drift velocity of majority charge carriers that is the whole study of a semiconductor can be done through this effect. Hall effect is widely used in various fields for a variety of applications. In almost all cases, a Hall effect sensor is employed. Let us now see these applications in detail. The first application is, from Hall effect we can determine the type of semiconductor. The Hall coefficient is negative for n-type semiconductor and positive for p-type semiconductor. Therefore, the sign of the Hall coefficient can be used to determine whether a given semiconductor is p-type or n-type. By measuring Hall coefficient, the carrier concentration in a semiconductor can be determined. For p-type semiconductor, majority charge carriers are holes. Therefore, R H is equal to 1 upon E into P. Therefore, concentration of holes is given by P is equal to 1 upon R H into E. In terms of Hall voltage, we can write down the formula as P is equal to I into B divided by V H into T into E, where T is the thickness of the semiconductor sample. Similarly, for n-type semiconductors, the electron concentration can be did in mind as n is equal to 1 upon R H into E. Next application is Mobility of charge carriers. Mobility is defined as drift velocity acquired in unit electric field. We know that the current density J is given by two equations. Now let us equate these equations and simplify then we will get the equation as mu is equal to sigma into R H, where sigma is the conductivity of the semiconductor sample. For drift velocity of the carriers, according to equilibrium condition, Lorentz force acting on the carriers due to applied magnetic field balances the force due to electric field. Now substituting these values, the equation for drift velocity can be V D is equal to V H upon B into W, where B is the applied magnetic field and W is the width of the semiconductor sample. Students now pause the video and try to solve this numerical. Check for the correct answers. N can be calculated by the equation R H is equal to 1 upon E into N and for mobility first calculate the conductivity from resistivity and solve. Next application is Measurement of magnetic field. Hall voltage is proportional to the magnetic field intensity for a given current through the sample. Therefore, one of the important application of Hall effect consists in measuring magnetic fields. Knowing the parameters of the Hall probe and applied current, we can determine the intensity of the magnetic field. In an electromagnetic wave, the electric and magnetic fields are mutually perpendicular to each other. If a semiconductor is held parallel to electric field E, it will cause a flow of current I in the semiconductor. As the semiconductor is subjected to a transverse magnetic field, at the same time, Hall voltage is produced in the sample. This Hall voltage is proportional to the product EH, which signifies the power of the wave. Also, Hall effect can be employed to measure the power of an electric wave. Hall sensors are useful for proximity switching, positioning, speed detection and current sensing applications, magnetometers, etc. A Hall effect sensor is a transducer that produces its output voltage in response to changes in magnetic field. Another contemporary application of Hall effect sensors are measuring wheel or rotor speed or rpm as well as determining position of camshaft in engine systems. These sensors are composed of a Hall element and a permanent magnet which are placed near a tooth disc attached to the rotating shaft. The gap between the sensor and a teeth of the disc is very small, so each time a tooth pass near the sensor, it changes the surrounding magnetic field which cause the output of the sensor to go either high or low. So the output of the sensor is a square wave signal which can be easily used for calculating the rpm of the rotating shaft. Next application, current passing through a semiconductor generates a magnetic field which changes with current. A Hall sensor can be used to calculate the current without breaking the circuit. They are specially used in measuring extremely heavy currents where conventional amateurs cannot be used. Smartphones are equipped with magnetic compass. The compass measures earth's magnetic field using 3 axis magnetometer. These magnetometers are sensors based on Hall effect. These sensors produce a voltage proportional to the applied magnetic field and also sense the polarity. The sensing of a wheel rotation is especially useful in anti-lock braking systems. An anti-lock braking system is a safety anti-skid braking system used on aircraft or on land vehicles such as cars, motorcycles, trucks and buses. ABS operates by preventing the wheels from locking up during braking, thereby maintaining tractive contact with the road surface, thereby maintaining tractive contact with the road surface. 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. In brushless motor, the rotor is permanent magnet. The coils do not rotate, but are instead fixed in place on the stator. With a BLDC motor, it is the permanent magnet that rotates. Rotation is achieved by changing the direction of the magnetic fields generated by the surrounding stationary coils. To control the rotation, you can adjust the magnitude and direction of the current into these coils. Automotive fuel level indicator, the main principle of operation of such indicator is position sensing of a floating element. When button magnet is mounted on the surface of a floating object, the current carrying conductor is fixed on the top of the tank, lining up with the magnet. As the level of fuel rises, an increasing magnetic field is applied to the current resulting in higher Hall voltage. The fuel level is indicated and displayed by the proper signal condition of Hall effect. This application of Hall effect sensor is spacecraft propulsion. A Hall effect thruster is a relatively low power device that is used to propel some spacecraft after it gets into orbit or further out into space. In the HET that is Hall effect thruster, atoms are ionized and accelerated by an electric field. A radial magnetic field established by magnets on the thruster is used to trap electrons which then orbit and create an electric field due to the Hall effect. A large potential is established between the ends of the electrons. A large potential is established between the end of the thruster where neutral propellant is fed and the part where electrons are produced. So electrons trapped in the magnetic field cannot drop to the lower potential. They are thus extremely energetic which means that they can ionize neutral atoms. Neutral propellant is pumped into the chamber and is ionized by the trapped electrons. Positive ions and electrons are then ejected from the thruster as a cosy-neutral plasma creating the thrust. Thank you.