Changes in Capacitance During Discharge of Parallel Plate Capacitor

[Captain Blue]

Homework Statement

I've been studying the changes in capacitance (presumably due to fringe capacitance) as a parallel plate capacitor discharges.

The data is entirely as I would expect, excluding the last few data points, which were taken at voltages less than two mV. The capacitance shows exponential decay until the roughly 2 mV point is reached; after this point, the capacitance increases rapidly.

Homework Equations

V = V(initial)*e^(t/RC)

The Attempt at a Solution

My primary speculation is that this anomaly is related to the resistor (5G ohm) and the low voltage.

Any suggestions would be appreciated.

 

[jbsteele]

The anomaly you are seeing is likely due to the effect of the resistor in the circuit. When the voltage across the capacitor drops below a certain threshold, the resistor begins to have an effect on the capacitance due to the current flowing through it. This current can cause the capacitance to increase, resulting in the observed behavior. To confirm this hypothesis, you can try increasing the resistance of the resistor and see if the effect is still present at the lower voltages. You can also try decreasing the resistance and see if the effect disappears.