LABORATORY 5
DC Circuits
Aim
To determine how the voltage across a capacitor increases with time when being charged
in an RC circuit. Acquire a basic understanding in using a CRO. Using the CRO to
investigate the charge and discharge curve of a capacitor in an AC circuit.
Introduction
To determine how the voltage applied acts in a capacitor circuit an experiment is
designed to charge and discharge the capacitor. In the charging cycle there is no current
until the switch is closed and then the charge begins. The voltage is measured across the
capacitor. Once the capacitor is charged the current stops flowing and the potential
difference reaches its maximum value, which is measured. As the capacitor is discharged,
it is done so through a 100ohm resistor.
When the CRO is connected to the capacitor circuit a square wave is used to rapidly
charge and discharge the capacitor. The CRO is setup to display both the input signal and
the voltage across the capacitor, simultaneously on the screen. From this display the
period and amplitude are measured.
Results
Observations
Peripheral conditions:
Room temperature: 24C
Time of experiment: 1100Hrs
Date of experiment: 25/05/18
Data Collection
See Appendix 1 for spreadsheet where data was collected, Theoretical charging,
Experimental charging values measured and calculated. This is done in 6 trials, each trial
is a different experiment as follows:
Trial 1 (s): 0
Trial 2 (s): t
Trial 3 (s): 2t
Trial 4 (s): 3t
Trial 5 (s): 4t
Trial 6 (s): 5t
This is done for the first 6 trials to show the change in voltage and current over time as
the capacitor charges.
Analysis
From the raw data captured, the experimental voltage and experimental current of each
trial are measured, as per Appendix 1.
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