second day 02/25/2016

Date: 02/25/2016

Kirchoff review, introduction to waveform, and how to use analog discovery

I. Kirchoff review:

Here we were given a circuit ( I believed this problem was from 4B class). Our goal was to find the potential of the middle resistor

For this problem, we actually used different approach. We assumed that the power source produced 50W, and all of the resistors would dissipate all of the power produced, using conseravtion of energy, we found the V_0 to be 20V

II. Introduction to Waveform:

We already installed waveform (and also Freemat on my laptop). Our goal now is to find relationship between current and potential by varying the potential using analog

1. First lab- predict how would the graph voltage v. current behave?

Test Trial- We checked to make sure that everything worked

Waveform 2015 version. The linear horizontal line of voltage indicated we were using the DC current

We checked the resistor- 102 ohms, our resistor's color was brown, black, brown, yellow, which was 100 ohms

Here is the data, Vs is the voltage from the analog discovery. Vr is from the multimeter. For this lab, our first attempt was to use two multimeters at the same time, but due to greater resistor value error( the more multimeters we used, the greater the perecent of the resistor), we only measured current and voltage one at the time.

Here are the two plots Vs vs. current and Vr vs current, notice that the resistor, at a point, would be 120 ohms if we take voltage/ current at that time

II. Definition-counting nodes, branches, and loops:

Node: the connection between two branches, the nodes are the conjunction, and the loop is a completion of a circuit

Here, we have 7 elements- therefore, we have 7 branches,5 nodes, and 3 loops

By applying Kirchoff Law, we able to find the  Vab=22V from I=6A

III. Mosfet Lab:

We were given the mosfet, our goal is to connect the mosfet in series with the analog and the multimeter.

Here is the setup. The DMM was connected to the resistor and to the left pin of the mosfet (and then connected to the red wire 5V). The middle pin of the mosfet was connected to the yellow female head, to read the G value. and the last pin was connected back to the circuit and the black female head (ground) 

2. Data Analysis

As we look at the graph, initially from 0 to 1.4, there was nothing happen, the mosfet now is just a regular piece of iron. As the voltage went to 1.5V, the electron started to "jump" to another pin, closing the circuit (Electron will jump with high enough potential- really similar to Hall Effect). After that, the current stayed constant

V. Conclusion:
Today we spent most of our time to study how to use Waveform program. At the first look, the Analog Discovery seemed to be complicated due to its many wires, but not too complicated after we figured things out. Eventually, I found it easy to set up circuit on the breadboard and adjust the voltage accordingly, much better than just using oscilloscope as we did in 4B