What email address or phone number would you like to use to sign in to Docs.com?
If you already have an account that you use with Office or other Microsoft services, enter it here.
Or sign in with:
Signing in allows you to download and like content, and it provides the authors analytical data about your interactions with their content.
Embed code for: RC Circuit Lab
Select a size
The RC Time Constant
Jeffrey Oghenevoke Omoniyodo
We want to investigate the time needed to charge and discharge a capacitor in a circuit, measure the voltage across a resistor as a function of time in an RC circuit as a means to determine the RC time constant, and to plot the graph of t(s) against V(v).
This experiment focuses more on capacitors and their capacitance. A capacitor stores charge. So we want to measure the time it would take the capacitor to charge with a specific maximum time in mind. We also want to measure the time it would take the same capacitor to discharge starting from the apex of the previously charged capacitor. The capacitance of a capacitor is defined as the charge divided by the voltage.
Literature Review and Equipment
- A voltmeter
- Crocodile clips and wires
- A power supply
- A circuit board
- A stop watch
Firstly, we some theoretical calculations were made in order to calculate the maximum time reached using the formula; Time(sec) = Resistance * Capacitance. For the first case, using the 100 kilo Ohms resistor. The maximum time was calculated to be 220 seconds. For the 49 Kilo Ohms, we got 107.8 seconds. Then the schematic diagram came into play. We built the circuit using the schematics. Connected the power supply, the capacitor, turned on the hand-held voltmeter and placed the 100 kilo Ohms in place. We recorded after every 10 seconds; so the maximum time for the 49K Ohms was rounded up to 110 seconds. We had three resistors, one 100K Ohms, one 39K Ohms, and one 10K Ohms. So the 10k and 39K was connected series so as to get the specified 49K Ohms.
Table 1: Charging of the 100K Ohms Resistor
Table 2: Discharging of the 100K Ohms Resistor
Table 3: Charging of the 49K Ohms Resistors
Table 4: Discharging the 49K Ohms Resistors
The idea was to have a 10-seconds interval until we reach 220 seconds. That is, after every 10-seconds, the voltage across the resistor was recorded all the way to 220 seconds; So we had a total of 22 trials. As the time increased the voltage across the 100 kilo Ohms resistor increased. We had a maximum 0f 7.04V measured within 220 seconds. For the 49 Kilo Ohms resistor, the maximum voltage reached was 7.38V within 110 seconds.
Then the capacitor was discharged starting from the apex (maximum voltage reached) of the previously charged capacitor. This was done with both the 100K Ohms connected and the 49K Ohms connected; but not connected on the same circuit board.
It was noticed that the longer It took to charge the higher the voltage across the resistors. Although during the discharging process, the voltage didn’t go to zero at the specified time. For the 100K Ohms, the minimum voltage reached at the end of the time was 2.802V, and for the 49K Ohms, it was 2.760V.
This was done to investigate the time constant in a RC circuit.