# Voltage and Current Laws in Multisim

Circuit Analysis – Week #1 Lab

Voltage and Current Laws in Multisim

PRELIMINARY LAB INSTRUCTIONS:

Use the following Lab Report Template (also found in Tools and Templates) when submitting your lab work.

Rules for lab submissions:

1. The lab document must be a Word document.  PDF files are NOT accepted.

1. All screenshots must be included.

1. All screenshots must include the Multisim time stamp.

1. Any and all Multisim files must be submitted.

1. Calculations must be provided when relevant to show how you arrived at any calculated numbers.

1. Any equations used must be typed in Word.  Copy and paste of equations from outside sources is prohibited.

1. No graphics are allowed in the Word document other than screenshots of circuits from Multisim with the time stamp.

1. The lab template must be used.  Specifically, it is brought to your attention that a summary MUST be provided explaining the results of the labs, the relationship of the results to expected results, and any challenges encountered. This is not a personal reflection on the lab but rather a professional five sentence or more summary of the lab.

Any violation of the submission rules above will result in a grade of 1.

BACKGROUND RESEARCH:

In preparation for the lab, research what resistance tolerance is and what causes is. Think about the impact resistance tolerance would have on measured values in a circuit. While resistance tolerance means that a given resistance will have a different resistance other than the ideal, it will not fluctuate over a short period of time. Think about these questions before starting the lab as it will help you in the analysis: Why then in a physical electrical circuit do the measurements fluctuate? What are the other factors involved? Is there anything else which effects the resistance value when placed in a circuit in a certain location?

LAB:

This week’s lab introduces you to the construction of a resistive network in Multisim and identifying the effect of tolerances. You will learn to utilize Multisim to confirm your calculations.

1. See the circuit below. For the load resistor of 7 KΩ, use the tolerance levels in the table to calculate ‘Vx’ to fill in the ‘Calculated Vx’ in the table below. When the tolerance is included in the calculation, the calculated Vx will be in the form x +/- y. (It should be noted that usually tolerance levels are not used in calculations. Rather, an ideal circuit is assumed, and it is expected that the measurements will not be exact due to the component tolerances.) Be sure to show your calculations, step by step (read rules above). Resistance Tolerance Calculated Vx (V) Measured Vx (V) Measured Vx (V) Measured Vx (V) Average Measured Vx (V) 7KΩ 7KΩ 5% 7KΩ 10%

1. Construct the above circuit in Multisim. If you need help with Multisim, refer to the tutorials in the Tools and Templates section. Please use the following documentation (also found in the Tools and Templates) if you need help setting up tolerances in Multisim. Use the Agilent Multimeter to make measurements.

1. Simulation:

1. Run simulation to measure the voltage drop across the 7KΩ resistor and record the measurements in the first box under ‘Measured Vx’ column. Take a time-stamped screenshot of the result.

1. Now, add the tolerances to the resistor based on the tolerances in the table and run the simulation to complete the table. Run the simulation three times in order to obtain three measured values for each tolerance. It is IMPORTANT to note that this variation in the simulation is NOT due to one resistor. In other words, it is as if the simulation takes out the resistor in the circuit, goes and gets another resistor out of the bin with the same tolerance, puts it in the circuit, and runs the simulation. Take at least one time-stamped screen capture for each tolerance level.

1. Analysis: In this section, you are to analyze your results. While the following questions MUST be answered, they may NOT be exhaustive nor represent all that you may want to look at. You may have other items you would like to address or calculate. You may have an idea to expand the table for the analysis to look at an additional item. You are free and expected to do that here as this is a minimum guide.

0. Calculate the average measured value for each tolerance level.

0. Do the measured values match the calculated values? If not, explain why they are different?

0. Explain the significance and the effect of adding resistor tolerances on your measurements of ‘Vx’ in Multisim?

0. Do the measured and average values seem reasonable in light of your calculated values? What is the relationship between the measured values and your calculated value?

0. While the simulation mimics changing out the resistor with a new resistor every time you run the simulation, it also reflects some of the variation one might experience with one resistor in a typical operating scenario. Why is that? What things besides tolerance effect the resistance value and measurements in real circuits? Explain at least one of those items in detail from the perspective of physics.

1. Create your lab report in a word document called “Lab1_StudentID.docx” with your GID substituted into the file name. Refer to the submission rules above. Be sure to include calculations, your analysis and answers to questions, screenshots, summary, etc.