Resistor-Capacitor Circuits c Robert DeSerio, 2017 University of Florida

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Resistor-Capacitor Circuits c Robert DeSerio, 2017 University of Florida Figure 1: The RC circuit showing the directions of the transient currents. Objective You will build resistor-capacitor... circuits and make measurements of the capacitor voltage as it charges and discharges through the resistor. The power source is the IOLab’s 3.3 V output and the voltages are measured by its voltage probes. Analysis of probe data will demonstrate the decaying exponential functions involved in the charging and discharging processes and provide an estimate of their time constant. Effective values for the capacitance of two capacitors in series and two capacitors in parallel will also be compared with predictions. Introduction The current in the dc circuits of previous experiments flowed at a steady rate. The current in the RC circuit of Fig. 1 flows only for a short time just after the switch is thrown. When the switch is thrown to the (a) position, the current Ia is in the direction shown and the capacitor charges until its voltage matches that of the supply, VS. When the switch is then thrown to position (b), the current Ib is in the opposite direction and the capacitor discharges. In both cases, the current quickly returns to zero. This temporary deviation from the steady state or equilibrium conditions reached afterward is called transient behavior and arises because of the charge-storing behavior of the capacitor and the currentlimiting behavior of the resistor. Theory Ohm’s law states that the potential change across a resistor is proportional to the current I flowing through it and decreases in the direction of the current. The proportionality constant is given by the resistance R. Vb - Va = -IR I -! Va 0B✂B✂B✂` Vb (1) When a charge Q flows into one plate of an initially uncharged capacitor, an equal amount [Show More]

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