Nodal Analysis with Multiple Sources

              

Prelab

constructed circuit

Voltage reading of 10k ohm resister

The voltage across V1 was 5V as it was in parallel with the 5V PS. To get the current across the 10k ohm resistor, we used AD to measured the voltage of that resistor and used Ohm's Law getting a value of 0.3201 mA. In the prelab, we got that value as a negative which only means we chose the opposite direction for that current when conducting our analysis.

Nodal Analysis 3

constructed circuit

Prelab

actual resistances

Measured value of V1

This time when we did our prelab, we used the actual resistances used in our constructed circuit vice the given values in the manual which deviate only a little. The theoretical value we got in the prelab was 2.459 V and the actual value we measured was 2.466 which gives us a percent error of 0.30 %. The value we get for I1 ends up being -0.266 mA which just means we chose the opposite of the actual flow of current when doing our prelab.

Nodal Analysis

Prelab

             

Measured readings

V2

V1

The percent error for V2 was 1.38% and for V1 was 3.42%. This was partly attributed to our actual resistance values not exactly the same as our theoretical ones.

Practical Voltage and Current Measurement

Using voltage divider, the Vout should be 2.5 V using an ideal voltmeter. In reality, a voltmeter will never be able to have infinite resistance and so could affect your readings if dealing with resistances that are close to the internal resistance of your measuring device. In the pic on the left, we used 10M ohm resistors. Since the DMM's internal resistance is 10M ohm as well, it ends up being in parallel with the 10M ohm resistor it's measuring, lowering the equivalent resistance of the two to 5M ohm. This changes the circuit causing only 1.666 V to drop across the resistor we were measuring. In the right photo, we used much smaller resistors, only 100k ohm. Since they were so much smaller compared to the internal resistance of the DMM, it was able to act as an ideal voltmeter and not distort the readings as happened previously.