hysteresis

/,histə'ri:sis/

Thân thiện

A magnet's hysteresis curve is plotted on a graph.

Definition

1. Noun:
   • The lagging of an effect behind its cause: A phenomenon where the response of a system lags behind changes in the force influencing it. This lag occurs because the system's state depends on its history.
   • Specifically in magnetism: The phenomenon where the magnetic induction (magnetization) of a ferromagnetic material, like iron, lags behind changes in the external magnetic field applied to it.

Usage and Examples

• General Scientific Context:

  • The control system accounts for hysteresis to ensure accurate positioning. (The system's design considers the lag between command and response.)
  • In economics, hysteresis can describe how high unemployment persists even after a recession ends. (The effect of unemployment lingers after its initial cause has diminished.)

• Physics and Engineering Context:

  • The hysteresis loop of the material was plotted to measure its energy loss. (A graph showing how magnetization lags behind the magnetic field was created.)
  • Mechanical switches often exhibit hysteresis to prevent chattering. (The switch has a built-in lag to avoid rapid, unintended on-off cycles.)

Advanced Usage and Concepts

• "Hysteresis loop": A closed curve, often seen on a graph, that shows the lagging relationship between two linked variables, like magnetic field strength and magnetization. The area inside the loop often represents energy loss.

  • The size of the hysteresis loop indicates how much energy is dissipated as heat in each cycle.

• "Thermal hysteresis": A lag in a physical property (like volume or phase) during heating and cooling cycles.

  • The protein's activity shows thermal hysteresis, being different at the same temperature depending on whether it was reached by heating or cooling.

• "Hysteresis loss": The energy lost, typically as heat, due to hysteresis effects in a material during a cyclic process.

  • Engineers select core materials with low hysteresis loss for efficient transformers.

Variants and Related Words

• Hysteretic (adjective): Relating to or exhibiting hysteresis.
  • The material's hysteretic behavior complicates the control algorithm.

Synonyms

• Lag: A delay between cause and effect. (More general, less technical)
• History dependence: The property where the current state depends on past states. (A descriptive synonym)

Related Phrases and Terms

• Magnetic hysteresis: The specific type of hysteresis observed in magnetic materials.

  • Magnetic hysteresis is a key principle behind the operation of permanent magnets and magnetic memory.

• Elastic hysteresis: The energy loss observed when a solid material (like rubber) is deformed and then returns to its original shape.

  • The tire's elastic hysteresis contributes to rolling resistance and heat buildup.

Notes on Meaning

• Core Concept: Hysteresis is fundamentally about memory or path-dependence in a system. The current output depends not just on the current input, but on the history of previous inputs.
• Contrast with Simple Lag: While similar, hysteresis implies a difference in the path when the influencing force is increasing versus when it is decreasing, often forming a loop. A simple time delay or "lag" may not have this path-dependent characteristic.

Học thuật

Noun

1. the lagging of an effect behind its cause; especially the phenomenon in which the magnetic induction of a ferromagnetic material lags behind the changing magnetic field