Lab Report Day Fourteen - Passive RC/RL Circuit Natural Response

Passive RC Circuit Natural Response Lab

In this lab assignment, we examine the natural response of a simple RC circuit. We use both a manual switching operation and a square wave voltage source to create our circuit’s natural response. We see that the method used to create the response affects the circuit being measured.







This is our RC circuit. In the pre-lab, we calculate the time constant for the circuit when there is no power source. We calculate our time constant to be 15.125 ms. In addition, we find that time constant has the same unit as time, which is s.



We build our circuit as shown. We measure our experimental value for R1 to be 0.98k, and R2 to be 2.14k Ohm, which is close to their theoretical value. I get our C value to be 22 uF. We assume our capacitance is accurate.




This is the set up of our circuit.




We use analog discovery to apply a 5V source ot the circuit. We get our oscilloscope graph as a linear part combined with a exponential part.





We know that e^-1 is about 0.3678, which means that after 1 time constant period, the value will be 36.78% of its original value. We have our initial value of 3.426. We calculate the voltage after one time constant is 1.260 V. We find the time difference is 49.5 ms, which is the experimental time constant. We have a % difference of -227%, which is very big.



In part b, we apply a 2.5 V square wave, and with a offset of 2.5 V at a low frequency. This way, we do not need to plug and unplug the power supply ourselves.

This is the graph we get when we apply a square wave.




In part B, we get maximum voltage of 3.432 V. Using the same method, we find experimental time constant to be 15.25 ms, with a % difference of -0.826 %, which is much accurate. This could be cause by the small difference of the theoretical and experimental value of resistor.

Analysis:
As we can see, when we apply a square wave at a low frequency, it has a low percent difference. I think it is because when we apply a square wave, we do not to plug and unplug ourselves. By plugging and unplugging, some current may loss and cause our part one has a high percent different (227%).

Passive RL Circuit Natural Response

In this lab assignment, we examine the natural response of a simple RL circuit. We will use both a manual switching operation and a square wave voltage source to create our circuit’s natural response. We will see that the method used to create the response affects the circuit being measured.




This is our pre-lab. We predict the graph when we apply a square wave with amplitude 2.5V and offset 2.5V to the circuit. We calculate two possible time constant, one is 10ns, and another one is 30 ns.



This is the set-up of this circuit,

Since we do not have time, Professor Mason does this lab for us.


This is his output graph. We can see that the graphs match. Our prediction is correct.

Summary:
Today we go over Capacitors and Inductors, and do labs on RC and RL circuits and learn how to solve RC and RL circuit problems.