# Transient Response of RC circuits

Objective

Plot the voltage across a capacitor, when it is charged by applying a voltage step through a resistor. Calculate the value of the capacitance from the graph.

Procedure

- From \emphElectrical , select \emphRCTransientresponse

- Click on 0->5V STEP and 5->0V step Buttons to plot the graphs

- Adjust the horizontal scale, if required, and repeat.

- Calculate RC time constant.

Discussion

Applying a 0 to 5V step makes the voltage across the capacitor to rise exponentially as shown in the figure. By fitting the discharge curve with , we can extract the RC time constant and find the values of capacitance from it.

The voltage across a capacitor is exponential only when it is charged trough a linear element, a resistor for example. When charged from a constant current source, the voltage shows linear increase, because , and voltage increases linearly with time as .