**ELECTRONIC PRINCIPLES - OD1647 - LESSON 1/TASK 1**

circuit. Curve A is a plot of both capacitor voltage during

charge and inductor current. during growth. Curve B is a plot

of both capacitor voltage during discharge and inductor current

during decay.

FIGURE 37. UNIVERSAL TIME CONSTANT CHART FOR RC AND RL

CIRCUITS.

The time scale (horizontal scale) is graduated in terms of the

RC or L time constants so that the curves may be used for any

R

value of R and C or I, and R. The voltage and current scales

(vertical scales) are graduated in terms of percentage of

maximum voltage or current so that the curves may be used for

any value of voltage or current. If the time constant and the

initial or final voltage for the circuit in question are known,

the voltages across, the various parts of the circuit can be

obtained from the curves for any time after the switch is

closed, either on charge or discharge. The same reasoning is

true for the current: in the circuit.

The following problem illustrates how the universal time

constant chart may be used.

**58**