In electrical engineering and mechanical engineering, a transient response is the response of a system to a change from an equilibrium or a steady state. The transient response is not necessarily tied to abrupt events but to any event that affects the equilibrium of the system. The impulse response and step response are transient responses to a specific input (an impulse and a step, respectively).

In electrical engineering specifically, the transient response is the circuit’s temporary response that will die out with time. It is followed by the steady state response, which is the behavior of the circuit a long time after an external excitation is applied.

The response can be classified as one of three types of damping that describes the output in relation to the steady-state response.

Transient response can be quantified with the following properties.

Oscillation is an effect caused by a transient stimulus to an underdamped circuit or system. It is a transient event preceding the final steady state following a sudden change of a circuit or start-up. Mathematically, it can be modeled as a damped harmonic oscillator.

Inductor volt-second balance and capacitor ampere-second balance are disturbed by transients. These balances encapsulate the circuit analysis simplifications used for steady-state AC circuits.

An example of transient oscillation can be found in digital (pulse) signals in computer networks. Each pulse produces two transients, an oscillation resulting from the sudden rise in voltage and another oscillation from the sudden drop in voltage. This is generally considered an undesirable effect as it introduces variations in the high and low voltages of a signal, causing instability.

Electromagnetic pulses (EMP) occur internally as the result of the operation of switching devices. Engineers use voltage regulators and surge protectors to prevent transients in electricity from affecting delicate equipment. External sources include lightning, electrostatic discharge and nuclear electromagnetic pulse.