ETYM New Lat., from Greek hysterein to be behind, to lag.
1. A retardation of the effect, when the forces acting upon a body are changed, as if from velocity or internal friction.
2. A temporary resistance to change from a condition previously invuced, observed in magnetism, thermoelectricity, etc., on reversal of polarity.
When an electrode system is returned to a solution, equilibrium is usually not immediate. This phenomenon is often observed in electrodes that have been exposed to the other influences such as temperature, light, or polarization.
The maximum difference between output readings for the same measured point, one point obtained while increasing from zero and the other while decreasing from full scale. The points are taken on the same continuous cycle. The deviation is expressed as a percent of full scale.
Lagging of an effect behind its cause.
Lag in the effect of a change of force, especially in magnetisation.
Phenomenon seen in the elastic and electromagnetic behavior of materials, in which a lag occurs between the application or removal of a force or field and its effect.
If the magnetic field applied to a magnetic material is increased and then decreased back to its original value, the magnetic field inside the material does not return to its original value. The internal field “lags” behind the external field. This behavior results in a loss of energy, called the hysteresis loss, when a sample is repeatedly magnetized and demagnetized. Hence the materials used in transformer cores and electromagnets should have a low hysteresis loss. Similar behavior is seen in some materials when varying electric fields are applied (electric hysteresis). Elastic hysteresis occurs when a varying force repeatedly deforms an elastic material. The deformation produced does not completely disappear when the force is removed, and this results in energy loss on repeated deformations.
The tendency of a system, a device, or a circuit to behave differently depending on the direction of change of an input parameter. For example, a household thermostat might turn on at 68 degrees when the house is cooling down, but turn off at 72 degrees when the house is warming up. Hysteresis is important in many devices, especially those employing magnetic fields, such as transformers and read/write heads.