PHY 156 4870
Lab Report #6: RC Circuits
October 14th, 2011
The purpose of this lab is to observe the charge and discharge curves of a capacitor and determine its time constant. The capacitor is observed with respect to the voltage traveling through the capacitor. Principles:
One of the main principles of this experiment is defined by V = VB [1 – exp (-t/RC)] for a charging capacitor and furthermore, τ is defined by resistance multiplied by capacitance(R * C). Thus, it is important to understand that as the capacitor is charged, over time the voltage will increase rapidly and eventually level off. Also, the other principle of this experiment is defined by by V = VB [exp (-t/RC)] for when a capacitor is discharging, thus the voltage will decrease rapidly over time and eventually level off as well before reaching zero. Apparatus & Procedure:
This experiment required the use of a 1.5 V D-size battery, a battery holder, a digital multimeter, a 220μF capacitor, a 100 KΩ resistor, a DPDT switch, connecting wires, alligator clips, and a stopwatch.
After the apparatus was set up and the multimeter was connected to the capacitor, the first procedure required the capacitor to be charged via throwing the switch towards the battery and simultaneously starting the timer. The voltage across the capacitor was recorded every 5 seconds until the voltage reached a value close the max voltage of the battery (max voltage = 1.52 V). The voltage values for every 5 seconds were plotted on the Y-axis of a graph against an X-axis of time.
After the capacitor was fully charged, the timer was reset to zero. The switch was thrown to the discharging position and the timer was simultaneously started. The voltage was recorded every 5 seconds as the capacitor discharged until it reached a voltage close to 0. The voltage values for every 5 seconds were plotted on the Y-axis of a graph against an X-axis of time. Results:
Results are attached....
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