Magneto Resistor – Symbol, Working, Types & Characteristics

Back in 1856, William Thomson a Scots-Irish mathematical physicist and engineer while experimenting with iron pieces discovered a phenomenon called magneto-resistance. This effect was later on used to build a special type of variable resistor known as magneto-resistor. In this article you shall get a brief about a magneto – resistor: its working principle, characteristics and applications. So let’s delve in! What is a Magneto Resistor? It was found by Sir William Thomson that, when the iron pieces were kept in magnetic feild, their electrical resistance somehow changed when the direction of magnetic feild with respect to the current flow through them changed. This effect was found when he experimented with nickel too. Thus a new effect or phenomenon was introduced to the world and it was named magneto-resistance. This effect was then further studied and a new type of variable resistor was formed. This resistor would have its electrical resistance vary with the magnetic field strength around it. The current through this resistor also changes with change in magnetic force applied to it. As you already know that magnetic field is a vector quantity meaning, it us specified in both direction and magnitude, just as a current. Thus, we can define a magneto resistor in one line as: “A special kind of variable resistor, whose electrical resistance depends on the external magnetic force applied to it.”   Magneto Resistor Symbol Schematically, in circuit diagram the magneto resistance is represented by the symbol shown below. The arrow through the resistor symbol signifies a variable resistor, while “x” below it denotes that the variable resistor used is “magneto resistor”   The working of the magneto resistor is quite easy; it is based on the effect already mentioned: the magneto resistance. Magneto Resistor – Working Principle To understand the working principle of a magneto resistor, let us first brush up our concept that relates the direction of current and that of magnetic force.   The magnetic field strength is highest, when the current is in same direction as that of the magnetic force, while weakest when it is 900 to the magnetic force. So how does this effect resistance of the material? The answer is simple. What is current? Current is nothing but flow of free electrons. When a material is placed in absence of any magnetic force, these electrons move in an orderly fashion, mostly in straight lines.   As soon as it is subjected to magnetic force, the free electrons get excited and start moving in an indirect motion creating collision among them. These collisions restrict the flow of free electrons such that only few can flow freely. This means the flow of current is restricted, that means the electrical resistance has increased with increase in magnetic field strength. Thus, to put in short terms, the resistance of a magneto resistor increases with increase in magnetic field strength and decreases with a decrease in magnetic field strength. According to the types of magneto-resistance effect, magneto resistor are also categorised into three groups. Lets discuss about them in brief. Magneto Resistor – Types #1. Based on Giant Magneto-resistance:-  Discovered by two scientists Albert Fert and Peter Grunberg, this effect is commonly observed in ferromagnetic materials. The resistance here depends on whether the adjacent ferromagnetic layers are in parallel or anti-parallel. If they are in parallel alignment then the resistance is low, while the resistance is high when they have an anti-parallel alignment.   #2. Based on Extra ordinary Magneto-resistance:- Discovered in 2000, this effect occurs in semiconductor hybrid systems under transverse magnetic field. The resistance of the semiconductor hybrid system increases under...
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