Unformatted text preview: lues of each current. CONCLUSION
Did your measured and predicted values of the currents through the resistors agree? If
not, explain the discrepancy.
As a check for the consistency of your measurements, calculate the potential difference
across each resistor using the currents that you measured. Compare these values with
the potential difference across each resistor that you measured with the DMM. 115 QUANTITATIVE CIRCUIT ANALYSIS (PART A) – 1302Lab4Prob9 116 PROBLEM #10: QUANTITATIVE CIRCUIT ANALYSIS
(PART B)
You apply for a summer job at an electronics company. As part of the interview
process, the manager gives you a circuit and asks you to calculate the current flowing
through each resistor. You are then given some batteries, resistors and wires, and asked
to build the circuit to check your calculation.
Instructions: Before lab, read the laboratory in its entirety as well as the required reading in the
textbook. In your lab notebook, respond to the warm up questions and derive a specific prediction
for the outcome of the lab. During lab, compare your warm up responses and prediction in your
group. Then, work through the exploration, measurement, analysis, and conclusion sections in
sequence, keeping a record of your findings in your lab notebook. It is often useful to use Excel to
perform data analysis, rather than doing it by hand.
Read: Tipler & Mosca 25.5. Pay attention to the examples 2510, 2514 and 2516. EQUIPMENT
You will have wires, resistors, and batteries
and a power supply to build a circuit shown to
the right. A power supply must be used for
one battery to vary the current.
You will have a digital multimeter (DMM) to
measure resistances, voltages, and currents. R1 +
 V1 R2 +
 V2 R3 +
 V3 C ircu it XIII Read the sections The Digital Multimeter (DMM) and Resistor Codes in the Equipment
appendix.
Read the appendices Significant Figures, Review of Graphs and Accuracy, Precision
and Uncertainty to help you take data effectively.
If equipment is missing or broken, submit a problem report by sending an email to
[email protected] Include the room number and brief description of the
problem. WARM UP
1. Draw a circuit diagram labeling all voltages and resistances. For this problem, the
voltages and the resistances are the known quantities and the currents in the resistors
are the unknowns. 117 QUANTITATIVE CIRCUIT ANALYSIS (PART B) – 1302Lab4Prob10 2. Assign a separate current for each leg of the circuit, indicating each current on the
diagram. Identify the number of circuit paths (loops) and label them on the diagram.
3. Apply conservation of current to each point in the circuit at which wires come
together (a junction). Use conservation of energy to get the sum of the potential
differences across all of the elements in each loop, ensuring your signs are correct.
Does the potential difference increase or decrease across each circuit element, in the
direction you have chosen to traverse the loop? Use Ohm's law to get the potential
difference across each resistor.
Check that the number of linear equations that you have now matches the number of
unknowns.
4. Complete the calculations and write your solution. Simplify your equations as much
as possible, but be warned that your final solutions may look quite complicated. PREDICTION
Derive formulas to calculate the current through each of resistors in Circuit XIII as a
function of voltages of the batteries and resistances involved in the circuit. EXPLORATION
If necessary, read about how to use the DMM in the appendix. Pay special attention to
the connections and settings that are used to measure voltages and currents, and why
the DMM should be connected in the circuit differently for voltage and current
measurements. Do you know why we should connect them in these ways?
Build Circuit XIII. How can you tell if there is current flowing through the circuit?
What happens to the current at each junction? What is the resistance of each resistor?
What is the potential difference provided by each of the batteries? What is the potential
difference across each resistor? Use the DMM to check your answers to each of these
questions.
Complete your measurement plan. MEASUREMENT
Measure the resistance of each of the three resistors, as well as the currents flowing
through each of them. Measure the potential difference provided by each battery. So 118 QUANTITATIVE CIRCUIT ANALYSIS (PART B) – 1302Lab4Prob10
that you can check your measurements, measure the potential difference across each
resistor. ANALYSIS
Calculate the current through each resistor from your prediction equations, using your
measured values of the resistance of each resistor and voltage of each battery. Compare
those results to the measured values of each current. CONCLUSION
Did your measured and predicted values of the currents through the resistors agree? If
not, explain the discrepancy.
As a check for the consistency of your measurements, calculate the potential difference
across each resistor using the currents that you measured. Compare these values with
the potential difference across each resistor that you measured with...
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This document was uploaded on 02/23/2014 for the course MANAGMENT 2201 at University of Michigan.
 Spring '14

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