Difference between revisions of "TF EIMLab1 Writeup"

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|Variable ||Measured Value|| Predicted Value|| % Difference
 
|Variable ||Measured Value|| Predicted Value|| % Difference
 
|-
 
|-
| <math>V_B</math> || 103.5 mV  || 156 || 50%
+
| <math>V_B</math> || 103.5 +/- 50 mV  || 156 || 50%
 
|-
 
|-
 
| <math>I_1</math> || 20.4 mA  ||22 || 7%
 
| <math>I_1</math> || 20.4 mA  ||22 || 7%

Revision as of 20:15, 12 January 2011

Kirchoff's Law (50 pnts)

Construct the circuit below

TF EIM Lab1.png


Enter the values of the DC voltage and Resisters that you used.

Use a voltmeter to measure the potential difference and resistances.

Variable Measured Value
VA 20 Volts
R1 902 Ω
R2 10.2 Ω
R3 10.6 Ω

Enter the measured and predicted quantities in the table below

Given VA and the values of all resistors, use Kirchoff's laws to predict

a.) Predict the value of VB

VAI1R1=Vb

I_1 =?

Kirchoff's Loop theorem (Voltage Law)

VAI1(R1+Rtot)=0 where Rtot =resistance for R2 and R3 in series.

Rtot=11R2+1R3=5.2Ω

I1=VAR1+Rtot=20Volts902Ω+5.2Ω=22mA


Vb=VAI1R1=200.022×902=156 mV

b.) Predict the values of the three currents.

I1=I2+I3

I2R2I3R3=0

2 equations and 2 unkowns

I3=I1R3R2+1=22mV10.610.2+1=10.8 mA

I2=I1I3=2210.8=11.2 mA

c.) compare your predictions and measurements by filling in the table below.

Variable Measured Value Predicted Value % Difference
VB 103.5 +/- 50 mV 156 50%
I1 20.4 mA 22 7%
I2 9.5 mA 11.2 18%
I3 9.0 mA 10.8 20%

Internal resistance (30 pnts)

Measure the internal resistance of your power source by graphing the potential difference on the x-axis and the current on the y-axis for several values of the resistance RL shown in the circuit below. Begin with RL=1kΩ and then decrease it by a factor of 5 for each subsequent measurement. You can use a volt meter to measure the current and potential difference.


TF EIM Lab1a fig.png


R_{Load} (Ω) V (Volts) I (mA)
10 1.42 ± 0.06 118 ± 3
93 1.55± 0.01 16.15 ± 0.05
990 1.575 ± 0.005 1.54 ± 0.04
10110 1.579 ± 0.005 0.146 ± 0.005
15060 1.579 ± 0.005 0.101 ± 0.003


Below I set R= 95 Ω and changed V

V (mv) I (mA)
126.1 0.79
300 2.64
500 4.62
1000 9.29
2000 18.78
3000 30.4

Now lets try to fix V and change R


Lab1a TF EIM.png

Questions (20 pnts)

  1. What conservation law is involved in Kirchoff's Loop Theorem?
  2. What does the slope in the internal resistance plot above represent?


TF_EIM_LabWriteups