Day 6 3/10 Mesh analysis and transistors

At the beginning of the class, we did a quiz about mesh analysis. 

In this photo, we use mesh analysis and create three equations and there are three unknown and we can find the i in each loop and find the I is 1.2A.

Then we learn MESH ANALYSIS WITH CURRENT SOURCES. The key is a supermesh results when two meshes have a (dependent or independent)
current source in common. 

In this photo, we use the mesh analysis with current sources and set up 3 equations and find the i1 =-2.57A and i2=-0.34A and i3=0.428A.

NODAL VS MESH ANALYSIS

In this photo, we list some different betwwen nodal analysis and mesh analysis.

Mesh analysis:
Networks that contain many series-connected elements, voltage sources, or supermeshes. a circuit with fewer meshes than nodes is better analyzed using mesh analysis.  
Nodal Analysis:
Networks with parallel-connected elements, current sources, or supernodes are more suitable for nodal analysis.   A circuit with fewer nodes than meshes is better analyzed using nodal analysis
The key is to select the method that results in the smaller number of equations. 

Lab： Mesh Analysis 2

Pre-lab question:

Purpose: the purpose of the lab is to use mesh analysis to calculate the theoretical voltage across 6.8k ohms and current I1. Then, compare the theoretical voltage and current with the experimental values. 

In this photo, we calculate the I1=-3.22*10^-4A and V1=-5V.

In this photo, we use the everycircle to see that if our solution is right. Then we find our data is right.

In this photo,We first measured the resistors in circuit and compare them with theoretical values.

In this photo, The set up of the circuit as the picture shown.

The picture shows the experimental value of V1 which is -5V and I1=-0.33mA

In this photo, here is a summary  of data and percent differences of voltage V1  and current I1. The percent differences of the voltage  is 0. the percent differences of the i1 is 3%. The error might be caused by the inaccuracy of resistors and some resistance in the wire.

Then we learn about Circuit Analysis of Transistors 

In this photo, we did an exercise about Circuit Analysis of Transistors and we find that V0=5.175V.

Lab 2: A BJT Curve Tracer 

Purpose: we need to find the collector current, and the relationship of IC vs. collector voltage, VCE characteristics of the BJT. The kit of parts the student has will contain a number of transistors.

In this photo, we find the true value of 100Kohm resistor which is 98.2 Kohm.

In these photos,the left one is NPN transisotr. the right one, it is the set up of the experiment.

In this photo, here are our first input wave (Channel 1) and second input wave (Channel 2).

In this photo.here is the oscilloscope of the wave it detected.

Summary:

In the beginning of today's class, we take a group quiz, and later on, we finish a mesh analysis lab. we learn about dioda and talked about the Transistors (NPN and PNP).  Now, we can use a lot of ways to solving circuit problems.Then we introduce BJT, and figure out how BJT works.