Transients

IN MANY instances the behaviour of a circuit or system is only of interest when it is in a steady state. There are occasions, however, when the temporary response of a circuit to a change in conditions is required. For example if a power supply in a circuit is switched on there may be a surge, possibly with oscillations, before a steady flow of current is established. One may wish to calculate the magnitude of the transient current to avoid damage to components. Circuits exhibit transients when they contain components that can store energy, such as transformers, inductors and capacitors; circuits that are purely resistive cannot display transient behaviour. Simple circuits containing only one type of storage element (that is RC and RL circuits) will be examined initially, followed by more complicated circuits that will be analysed with Laplace transforms.