Make-Up Prototyping Lab 4/23/2014

Prof Mason couldn't making it to class today so we used the time as Lab to finish up our unfinished Breadboard Lab from last week...

We first finished setting up the circuit on the breadboard by using a potentiometer as Resistor #2 and adjusted it until its resistance was roughly about 2.15 kΩ.  We tried our best for this value since the potentiometer was too sensitive to adjust to an exact value of  2.00 kΩ.

The potentiometer (wiper-like element) is essentially a voltage divider for measuring electric potential

We then measured the resistance across resistors R_1, R_2, R_3, the potential differences (voltage), and currents i_1, i_2, and i_3. The data is as follows:

As the measured data shown above, the percentage discrepancy was extremely large as high as 130% for the third resistor.  Based on this observation, we conclude that the huge source of error is in the potentiometer due to the extreme sensitivity & difficulty to adjust.

Next, we ran the experiment again, except this time, we swapped the potentiometer with a resistor that had a measured resistance of 2.13 kΩ in beige-tan..

According to the new measurements, we can see that values were much more accurate than the previous attempt. Though better accuracy, however, the resistors still did not match the theoretical resistances that we had used to calculate the theoretical currents. We conclude the largest sources of uncertainty were in the resistors and the battery.  For instance, the battery alone provided 1.45 V instead of 1.50 V. The percentage discrepancy is still as high as 8.7%