To determine the time constant of an RC circuit
- To learn the concept of half-life associated with the exponential function
- To learn how to plot an exponential function along a log scale so that the graph is a straight line
- To learn how to use spreadsheet to record, plot, and analyze experimental data
- Breadboard, a 1,000-Ω resistor, 0.1-μF capacitor
- Universal 850 Pasco Interface with voltage sensor
- Two wires to connect the breadboard to the Pasco interface for power
Use 1,000-Ohm resistor with 0.1 microF capacitor to connect in a RC circuit. Connect the breadboard to the Pasco interface for power and turn the interface on (green light)
In Pasco Capstone:
- Click on the input where you connected the voltage sensor and select voltage sensor from the drop down menu
- Click on the upper right corner input (power) and select output voltage current
- Click on the signal generator icon (bottom of the left menu) and select positive square function with 2000 Hz frequency and 10 V amplitude.
- Click on the bottom part of the window to change the measuring frequency to 500 kHz
- Click on the bottom of the screen (recording conditions) and select “end conditions” time 0.001 s
Activity 1. Determine the time constant of an RC circuit
Measure the voltage across the resistor as a function of time. Export data for one segment during the voltage drop into spreadsheet. Plot ln V versus time and determine the slope. What is the time constant of the circuit? How does it compare with the values given by the manufacturer.