Essay on RC Circuits Lab Report

1490 Words Nov 18th, 2013 6 Pages
Experiment 5: RC Circuits

Abstract

The purpose of this lab is to learn and understand RC Circuits. An RC circuit is composed of at least one resistor and at least one capacitor. A capacitor is composed of two plates with either air or an insulator also known as a dielectric between the plates. We do not want the plates to be touching, because then we would only have a conductor. The insulator between the plates is also known as the dialectic, which affect how the capacitor will store charge. In an RC circuit, voltage will flow from the battery to the capacitor and through the resistor. When the capacitor is charging, the voltage across the battery is decreasing until the capacitor is fully charged. When the
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For the RC circuit with one capacitor and one resistor, we calculated the theoretical time constant to be 100 microseconds, because we know the values of resistance and capacitance. So, we used the formula . We estimated the half time to charge and discharge of the graph on the oscilloscope and then use the formula, τchrage = τdischrage = to find the time constant for charging and discharging. Then we used the average of those two time constants to compare with the theoretical time constant. The percent difference between the theoretical and observed time constant is 9.5%.
For the RC circuit with two capacitors in parallel, we expected a greater equivalent resistance, because the capacitances are additive when they were arranged in a parallel manner. So the theoretical equivalent capacitance is equal to 2.0±0.3 microfarads. The half time for this RC circuit to charge and discharge is 150 microseconds. So the time constant for this RC circuit is 110 microseconds. Then using , the capacitance is calculated to 2.20micro-Farad. Comparing the theoretical value to the observed value, we calculated the percent difference to be 9.5%. The percent difference was not significant, so using the oscilloscope to find the time constant is a fairly accurate way to calculate the observed capacitance.
For the RC circuit with two capacitors in series, we expected the equivalent capacitance to be lower than the equivalent capacitance of two capacitors in parallel. By

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