Considering transients in electrical circuits, one cannot but note the fact that such phenomena are quite natural and to some extent predictable. Moreover, each person is faced with their manifestation in their daily lives. For example, for a heating element included in the network (electric heating elements, oil heater), the temperature does not rise infinitely, but to a certain value, depending on a number of factors: such as ambient temperature, humidity level, wire characteristic, etc. Accordingly, cooling occurs to some steady-state value, and not to absolute zero. In other words, all physical phenomena can be conditionally divided into transient and established ones. The former is a change between the initial and the final steady.
What are transients in electrical circuits? When analyzing any circuit, two possible operating modes must be taken into account: steady-state and transient. The first is characterized by instantaneous values of alternating current and voltage repeating per unit time in all parts of the circuit. Transients in electrical circuits are easier to understand: when such changes stop, then we can talk about the onset of the steady state. The corollary is as follows: a state in which there are no changes, theoretically, an unlimited time can last.
Transients in linear electrical circuits are familiar to everyone. Surely, it happened to everyone that after clicking the home switch, the lamp burned out or even the glass bulb itself shattered into fragments. Moreover, this can happen both with budget lamps and with expensive branded ones. This is the “guilty" transient in electrical circuits. In this case, that click of the switch caused the changes, initiated a transition process called switching (i.e. switching). In fact, the reasons may be different: changing the parameters of the power source, in particular a short circuit, external influences (magnetic field, temperature), etc. Direct calculation of voltage and current changing per unit time is possible by compiling differential equations and calculating the integral. In the formulas, the number of derivatives directly depends on the elements of the chain itself.
Since the duration of the transition process is usually calculated not even in seconds, but in hundredths and thousandths of a second, sometimes the question arises of the appropriateness of the calculations. Indeed, what can happen in such a short time? Alas, this is only partly true, and practice shows that quite a lot. For example, the power contacts of the starters are always designed for a much larger current than the rated current. In addition, contacts are often closed by arcing chambers (gratings). This is due to the fact that at the time of switching (switching on / breaking the circuit), the current increases tenfold, and to eliminate possible consequences, these solutions are applied.
Consider transients in rc circuits. For example, take a circuit consisting of a power source, a pair of resistors (R1 and R2), a capacitor (C) and a voltmeter (V) connected in parallel. If the capacitor used has a capacity of tens of microfarads, and the resistance R1 and R2 are a couple of hundred kilograms respectively, then when the source is turned on, the voltmeter arrow does not immediately indicate the actual voltage value, but gradually deviates from zero. This transient is due to the accumulation of charge in the capacitance. Accordingly, the steady state occurs at the moment when the consumption of the reactive component ceases.