Magnetic Hard Drives

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Magnetic Hard Drives The essence of a magnetic hard drive is to store data on it in binary form. The main components of a hard drive consist of a platter (disk), head, actuator and actuator arm. The actuator arm supports a head, which is an electromagnet that scans over the disk and either writes data by changing the magnetization of specific sections on the platter or it just reads the data by measuring the magnetic polarization. A voice coil actuator is used to move and position the arm with great control and precision. The base of the actuator arm is connected to the voice coil actuator. The arm sits between two powerful magnets, that move’s due to a Lorentz Force. The Lorentz Force states that when you pass a current through a wire that is in a magnetic field, the wire experiences a force and reversing the current will also reverse the force. As current flows in one direction in the coil, the force created by the permanent magnet makes the arm move one way, and reversing the current makes it move back. The force in the arm is directly proportional to the current through the coil, which allows the arm’s position to be finely tuned. At the end of the arm, lies the most critical component; the head, it’s a piece of ferromagnetic material wrapped with wire. As it passes over magnetized sections of the platter, it measures changes in direction of the magnetic poles called Faraday’s Law. Faraday’s Law states that a change in magnetization produces a voltage in a nearby coil. As the head passes a section where the polarity has changed, it records a voltage spike; the spike both negative and positive represents a one and when there is no voltage, the spike corresponds to a zero. As the head gets closer to the platter, its magnetic field covers less area, which allows for more sectors of information to be packed on the disk surface. To keep a critical height between the

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