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| Learn More | Actuator Design: Hysteresis |
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| What is Hysteresis? |
Hysteresis, in its simplest formulation, is a loss of energy in a material during cyclic excitation. The simplest example of this phenomenon is seen in ferromagnetic materials.
When exposed to a varying magnetic field a ferromagnetic device will exhibit a magnetization behavior (a stereotypical hysteresis behavior) like that shown in the figure below.
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| An example explained |
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| Fig 1. |
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As the magnetic field in the material rises the magnetization curve travels along the upper curve the from point "a" to point "B".
When the applied magnetic field reaches 3.0 H/J it is arbitrarily decreased. As the magnetic field decreases the magnetization of the ferromagnetic material traces the lower path to point "C" and "D".
Put simply, the material's demagnetization curve does NOT retrace the magnetization curve. This difference is called the material's magnetization hysteresis and it represents a "loss" of energy in the process.
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| What happens to the energy "lost" during hysteresis? |
In the example listed above, the energy is lost in the form of heat. For most processes, the energy lost to hysteresis leaves the system in the form of heat. It is interesting to note that we commonly use the term "lost" with reference to the energy released during a hysteresis effect.
In the field of Thermodynamics the energy released in a hysteresis cycle is not considered lost, it is taken as a measure of the work done by the system.
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