### Types of processes

*or*

__step____upset__*(a change from one level to another in supposedly zero time) in the input of the system. Now we start examine how the output of the system (voltage of the capacitor) changes with respect to time. Then, if we measure values of a voltage of the capacitor Uc at various times and plot them vs time, we’ll get the curve shown in Fig.1.3a. To get more accurate picture we present this curve in the scale (see Fig. 1.4).*

__step change__*necessary for the capacitor to charge to the 63.2% of the battery voltage (no matter what is the battery voltage) is*

__time interval__*for any one value of the resistance (R) and the capacitance (C). This time is called the*

__constant__*. To get the value of the time constant we must multiply the values of resistance and capacitance.*

__time____constant__*s*.

*. In the case presented in Fig.1.4 the time constant is equal 20 sec. It means - the voltage of the capacitor will be equal to 63.2% of the battery voltage after 20 sec will have passed from the beginning of a charging process. For example, if the battery voltage is equal to U*

__second___{B }= 50V then after 20 sec the voltage of the capacitor will be equal to Uc = 31.6V.

*. The curve in Fig. 1.4 is called a*

__transient process__*. The form of this curve is*

__reaction curve__*, and sometimes the curve is called*

__exponential__*The capacitor never will charge to the same voltage as the battery, but after t ≈ 4.6 seconds the former will charge to 99% of the battery voltage. This time we can accept as the end of the transient process.*

__exponential-transient curve__.

*of a system defines behaviour of a process in respect to time (see Fig. 1.3 and Fig. 1.4).*

__Dynamic characteristic__

*of a system defines behaviour of a process which does not involve time or which takes place over a sufficient length of time that dynamic changes become of minor importance. Static characteristics can be of linear and non-linear character.*

__Static characteristic__Article Source: Dr. Alexander Badalyan, University of South Australia