Lab 4

1. (Table and graph) Use the transistor by itself. The goal is to create the graph for IC (y axis) versus VBE (x axis). Connect base and collector. DO NOT EXCEED 1 V for VBE. Make sure you have the required voltage value set before applying it to the base. Transistor might get really hot. Do not TOUCH THE TRANSISTOR! Make sure to get enough data points to graph. (Suggestion: measure for VBE = 0V, 0.5V, and 1V and fill the gaps if necessary by taking extra measurements).

VBE (V)	Current (mA)
0.070	9.8
0.175	22.7
0.336	44.1
0.500	66.7
0.732	83.0

Table 1: This table shows the growth of IC compared to the growth of VBE

Graph 1: This VBE and IC graph illustrates the exponential increase in the transistor

2. (Table and graph) Create the graph for IC (y axis) versus VCE (x axis). Vary VCE from 0 V to 5 V. Do this measurement for 3 different VBE values: 0V, 0.7V, and 0.8V.

Graph 2: This shows the distribution of the the VCE, VBE and IC tables

VCE (V)	VBE (V)	IC(mA)
0.714	0.823	74.4
1.024	0.823	130
1.485	0.823	155
2.016	0.823	241

Table 2: This table  shows how IC varies with the fluctuation of VCE while VBE stays the same at .8V

VCE (V)	VBE (V)	Ic (mA)
.7	.716	12.25
.972	.716	13.25
1.44	.716	14.05
2.114	.716	15.48
2.941	.716	18.7
3.971	.716	24.4

Table 3; This table shows how IC changes with VCE changing and VBE staying stable at .7V

VCE (V)	VBE (V)	IC(mA)
0-5 *	0	0

*With any value of V_CE, I_C= 0
Table 4: This table shows when VBE is zero, Ic also stays zero no matter the voltage from VCE

3. (Table) Apply the following bias voltages and fill out the table. How is IC and IB related? Does your data support your theory?

VBE (V)	VCE (V)	Ic (mA)	Ib (mA)
.7	2	12.9	2.7
.75	2	53.3	7.2
.817	2	82.8	16.4

Table 5: This table shows the relation between IC and IB while VBE changes and VCE remains stable

IC is fairly consistently a multiple of IB, which is consistent with our theories based on the purpose of the transistor: to amplify current. Therefore, it makes sense for the current at the collector to be higher than that at the base.

4. (Table) Explain photocell outputs with different light settings. Create a table for the light conditions and photocell resistance.

Lighting	Resistance (kΩ)
No Light	7.1
Partial Light	5.15
Room Light	1.73
Flash Light	.745

Table 6: This table shows how diffent shades of light affect the photocell


The photo resistor is a resistor of varying values depending on the amount of light on it. The higher input of light, the lower the resistance value. Moving forward this will mean that light on this photocell will allow the motor to run, while less light would slow it down or stop it all together.


5. (Table) Apply voltage (0 to 5 V with 1 V steps) to DC motor directly and measure the current using the DMM.

Voltage (V)	Current (mA)
.082	6.22
.92	30.2
1.969	39.3
2.962	43.5
3.95	49.6
5.05	54.9

Table 7: This table shows the increase in current as the voltage increases

6. Apply 2 V to the DC motor and measure the current. Repeat this by increasing the load on the DC motor. Slightly pinching the shaft would do the trick.

The more load on the motor the higher the current would spike to keep the motor rotating. However since the motor is quite small the motor ends up stopping at about 125 mA.

7. (Video) Create the circuit below (same circuit from week 1). Explain the operation in detail.

Video 1: This video explains the process happening during the Rube Goldberg circuit set up

8. Explain R4’s role by changing its value to a smaller and bigger resistors and observing the voltage and the current at the collector of the transistor.

Resistance (Ω)	Voltage (V)	Current (mA)
0	10.2	31.2
47	10.2	31.0
390	10.2	25.6
1.2k	10.2	8.64

Table 8: This table demonstrates how the change in resistance for R4 will affect the current

R4 reduces the current going through the collector of the transistor. A higher resistance will lower the current through the transistor and the motor in accordance with ohm’s law. 

9. (Video) Create your own Rube Goldberg setup.

Video 2: Our Rube Goldberg created in class