Day 6

Today we had a fiesta at the beggining of class, worked a little more on mesh analysis with a lab, and learned about diodes and transistors. 

Here we had our 10 minute fiesta where we used mesh analysis to find the currents in the circuit. 

We then worked on mesh analysis that included a current supply. Mesh analysis allows us to negate that branch when we use KCL. Then use junction rule to get the third equation for 3 equations and 3 unknowns.

The objective of the Mesh Analysis III lab is to use mesh analysis to determine I1 and V1 as shown below, then build the circuit and compare with measured values. 

Through mesh analysis, we calculated I1 = 0.260mA and V1 = 2.46V. 

Here is the schematic of our circuit. The green and yellow wires were used to connect the DMM to measure current. The meter shows a negative current because the polarity of the meter was accidentally switched.

Here we are measuring the voltage across the 22k ohm resistor.

As shown in the third picture of this post, our percent error of current and voltage were quite small. Due to the way the DMM measures current and its efficiency, there is always a larger uncertainty in current measurements than voltage measurements which getting a larger error on current seems expected. Also, we assumed the resistances used are exact as marked.

Here we show which type of analysis makes the math easier based on the diagrams shown above.

Here we learned how to redraw the circuit to model the transistor in order to find the current going in the base of the BJT and the voltage across it. Transistors are modeled as shown in the upper right corner of the above picture.