Capacitor Voltage-Current Relations Lab

Capacitor Voltage-Current Relations Lab

Overview: In this lab we measured the relationship between the voltage difference across a capacitor and the current flowing through it. Using several time-varying signals to a circuit containing a capacitor and resistor in series, all aspects of the voltage and current through the capacitor should be able to be analyzed.

Design: We designed the following simple circuit:

In our circuit, we used a value of the resistor equal to 100 Ohms, and had a capacitor capable of storing 1 microFarad. We also used a function generator for our Vin with three different settings: two sinusoidal waves with magnitudes of 2 V and frequencies of 1 and 2 KHz respectively, and one triangular waves with magnitude 4V and a frequency of 100 Hz.

Because the current is equal to dv/dt, we anticipated the oscilloscope to detect Voltages (blue) and currents (red) as such:

Results:

Oscilloscope window for Sinusoidal wave with frequency of 1KHz:

 Oscilloscope window for Sinusoidal wave with frequency of 5KHz:

 Oscilloscope window for Triangular wave with frequency of 100 Hz:

Analysis: As the screenshots illustrate, our predictions match the outcome. We also included a match function on the oscilloscope window to execute the calculation of current through the capacitor (in mA). As expected, the current through the capacitor is phase shifted 90 degrees, and it is directly proportional to the resistor (in our case only differing by +/- .89% from the calculated value, which is phenomenal).