What type of response characterizes "hysteresis" in a control system?

Hysteresis in a control system is characterized by a time-lagged response due to the system's memory effects or the lag with which it responds to changes in input. When a control variable changes, the system does not respond instantaneously to that change but rather exhibits a delay or lag in its output. This is particularly evident in systems where the output depends not only on the current input but also on the history of past inputs.

In practical terms, hysteresis is seen in situations such as mechanical systems with friction, magnetic materials, or thermal systems where the state depends on previous conditions. The presence of hysteresis means that the system will have different output values for increasing and decreasing inputs, creating a looped response on a graph—indicating the time-lagged effect.

In contrast, a linear response suggests an immediate and proportional output change in response to input, which does not align with hysteresis behavior. Constant oscillation refers to repeated and predictable fluctuations, while an immediate reaction means that the output follows the input closely without delay. Thus, the defining characteristic of hysteresis in control systems is indeed the time-lagged response.