ETY155 Lab05 Parallel Circuit Measurements Winter 2021 PDF

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Parallel Circuits...

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ETY155 – L05 – Parallel Circuits Measurements (Week 4) Name:

Lab Section:

Components/Apparatus Required for this Lab 

The full ETY parts kit and organized component box

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The full LIN toolkit, including toolbox and all the hand tools

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Make sure you definitely have these components:

Lab Overview

o

1 breadboard and 10 jumper wires

Last week you practiced taking the resistance, voltage, and current measurements of resistive series circuits on a breadboard.

o

4 fixed resistors: 2.2 kΩ, 5.6 kΩ, 6.8 kΩ and 8.2 kΩ

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The Digital Multimeter or “DMM”

This week you will take VIR measurements on parallel circuits.

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The DC Power Supply (9 V battery)

Students often find parallel circuits to be a little harder to construct and to take measurements from because of the way they are built on the breadboards. Make sure you use jumper wires to spread out the circuit and build in space for accessibility. Refer to Lab 3 page 7 again for sample parallel circuit layouts.

Lab Code of Behaviour: http://inside.senecacollege.ca/semet/code-of-behaviour Below are highlights from the first week’s safety review: 1. Students are expected to conduct themselves in a professional and safe manner at all times.

Lab Outcomes

2. Food or drink is not allowed at any time.

1. Construct simple parallel circuits (2-3 Rs) on the breadboard. 2. Practice safety precautions while using the DC power supply and while making changes to a breadboard circuit.

3. Safety glasses are mandatory when the power is ON. 4. Failure to comply with the SEMET Electronics Laboratory Code of Behaviour will result in a lab grade of zero (0).

3. Set up the DMM as an Ohmmeter, Voltmeter, and Ammeter. 4. Measure resistance, voltage, and current for a parallel circuit using the correct settings on the DMM and placements on the breadboard. 5. Observe VIR characteristics of a parallel circuit and use appropriate laws to confirm the measurements.

Additional Safety Precautions in this Lab 

Disconnect the battery when making changes on the breadboard or to the DMM.

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PART A: Lab Preparation (Do this before attending the lab)

3. Write two different formulas that will calculate total resistance of a parallel circuit with 2 resistors.

1. Watch the video Circuit Design: Series vs. Parallel http://youtu.be/RvO76ycALCQ Note: Stop the video at time = 2:26. (Series-Parallel circuits will be discussed in next week’s Lab 6 in more detail.) 2. Consider a parallel circuit with the following components: 

DC power supply: E = 9.0 V



2 resistors: R1 = 5.6 kΩ, R2 = 6.8 kΩ

a) Draw this circuit diagram. Label all the parts. Indicate the current directions and voltage drops in the circuit.

4. Consider a parallel circuit with the following components: 

DC power supply: E = 9.0 V



3 resistors: R1 = 5.6 kΩ, R2 = 6.8 kΩ, R3 = 8.2 kΩ

a) Draw this circuit diagram. Label all the parts. Indicate the current directions and voltage drops in the circuit. Circuit B:

Circuit A:

b) On a separate sheet of paper, provide your full solutions to calculate all the VIR values in this circuit. (Keep 4 sig.figs.) b) On a separate sheet of paper, provide your full solutions to calculate all the VIR values in this circuit. (Keep 4 sig.figs.)

c) Place your final answers in this VIR summary table. Circuit B

c) Place your final answers in this VIR summary table.

V (V)

I (μA)

R (kΩ)

R1

5.6

R (kΩ)

R2

6.8

R1

5.6

R3

8.2

R2

6.8

Total

Circuit A

Total

V (V)

I (μA)

9.0

9.0

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RECAP: The Ammeter

PART B: Lab Exercises (Do this during the lab) 

Review the voltmeter and ammeter setups on the DMM.

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DISCONNECT the battery before inserting the meter.

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To measure current values, set the DMM to an ammeter.

RECAP: The Voltmeter 

To measure voltage values, set the DMM to a voltmeter

To set up the Ammeter function on the DMM: 1) Insert the red lead into the red jack marked: V •Ω••mA 2) Insert the black lead into the black jack beside it: COM 3) Change the function setting to 200m . To set up the Voltmeter function on the DMM:

Check the meter’s direction: Place the Red lead on the path closest to the Positive side of the power supply.

1) Insert the red lead into the red jack marked: V •Ω••mA 2) Insert the black lead into the black jack beside it: COM 3) Change the function setting to 20 VDC

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Gather and Check Your Resistors (10 mins) 1. From your Component Box, find the following resistors: a) R1 = 5.6 kΩ

Hint: R1 starts with Green.

b) R2 = 6.8 kΩ

Hint: R2 starts with Blue.

c) R3 = 8.2 kΩ

Hint: R3 starts with Grey.

2. Measure and record their resistances with the Ohmmeter. Record at least 4 decimal places. Are they “good” resistors?

Remember to turn OFF the power supply output when you make changes to your breadboard or DMM settings. Parallel Circuit A – Voltage Measurements (10 mins) 4. Remove the Ohmmeter from the circuit completely. 5. Attach the power supply to the two jumper leads at either end of the parallel Circuit A. 6. Set up the DMM as a voltmeter to measure voltage.

Expected or Nominal Value

Ohmmeter’s Measurement

Deviation %

7. Use the voltmeter to measure the voltages around Circuit A. a) Place the voltmeter in parallel across each component.

R1

5.6 kΩ

b) Record your findings in the table below.

R2

6.8 kΩ

c) Turn OFF the power supply in between each change.

R3

8.2 kΩ Circuit A

Percentage Deviation

Measured-Expected Expected

R1

X 100

R2

Parallel Circuit A – Resistance Measurements (15 mins) 1. Place R1 and R2 on the breadboard to make parallel Circuit A. Use jumper wires to space the resistors apart.

Voltage Measurements

Total 8. Compare your measured results from the previous step to the pre-lab calculated values for Circuit A. Do they match?

Remember to use Lab 3 page 7 for reference if you need help. 2. Insert jumper wires at either end of this parallel circuit. 3. Measure the total resistance of this parallel circuit. a) Record this measurement: b) Does this measurement make sense? Explain.

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Parallel Circuit A – Current Measurements (20 mins)

CAUTION: If you blow your fuse while measuring current, watch this video How to replace a fuse?

13. Compare your measured results in the previous step to the pre-lab calculated values for Circuit A. Calculate and record their deviations in this table. Were your results successful? Expected Current

9. Remove the voltmeter from the circuit completely. 10. Make sure disconnect the battery. 11. Set up the DMM as an ammeter to measure current. 12. Use the ammeter to measure the currents around the circuit.

Measured Current

R1 R2 T

a) Place the ammeter in series after each component. b) Record your findings in the table below. c) Disconnect the battery in between each change. Circuit A

Current Measurements

R1 R2 Total

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Deviation %

Parallel Circuit B – Resistance Measurements (5 mins) 1. Leave Circuit A in place on your breadboard. 2. Add R3 into Circuit A to make the parallel Circuit B.  Circuit B has 3 resistors in parallel: R1, R2, and R3. Remember to use Lab 3 page 7 for reference if you need help.

Parallel Circuit B – V & I Comparisons (20 mins) 7. Compare your measured results in the previous step to the pre-lab calculated values for Circuit B. Calculate and record the deviations in these tables. (Review the deviation formula.) Voltage:

3. Insert jumper wires at either end of this parallel circuit. 4. Measure the total resistance of this parallel circuit. a) Record this measurement:

R1

b) Does this measurement make sense? Explain.

R2

Expected Voltage

Measured Voltage

Deviation %

Expected Current

Measured Current

Deviation %

R3 T Parallel Circuit B – V & I Measurements (20 mins)

Current:

5. Attach the power supply to the two jumper leads at either end of the parallel Circuit B. 6. Set up the DMM first as a voltmeter to collect all the voltage measurements in the circuit, then as an ammeter to collect all the current measurements in the circuit. Record all of your measurement readings in the table below. Circuit B R1

Voltage Measurements

Current Measurements

R1 R2 R3 T 8. Were your results successful? Explain.

R2 R3 Total

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PART C: Bonus Exercises (Do this after finishing Parts A+B)

End of Lab Checklist



After completion of this lab, check off all the skills you can perform with confidence and regularity.

For this part, you will analyze the parallel Circuit B on your breadboard, comprised of E, R1, R2, and R3.

1. Check and record the total resistance of Circuit B again. Record this measurement: 2. Is there one fixed resistor in your Component Box that could replace the total resistance of the parallel Circuit B?

Safety: The Power Supply and The DMM

□ Understand the safe setup and usage of the power supply. □ Know how to measure the voltage output of the power supply. □ Disconnect the power supply when making circuit changes.

a) Find this resistor now. What are its 4 colour bands? Parallel Circuits – Resistance Measurements b) Measure the value of this resistor:

□ Measure the resistance of individual resistors.

c) Why is this a good replacement? Hint: Deviation.

□ Build a parallel circuit with 2 or 3 resistors. □ Understand the pros and cons of different breadboard layouts. □ Measure the total resistance of a parallel circuit.

3. Place the power supply across this single resistor. 4. Record the voltage and current from this equivalent Circuit C: Circuit C

Voltage

Current

Parallel Circuits – Voltage Measurements

□ Understand the safe setup and usage of the voltmeter. □ Place a voltmeter to measure voltages in a parallel circuit. □ Measure voltage for resistors in a parallel circuit.

Total 5. Were your results successful? Explain.

Parallel Circuits – Current Measurements

□ Understand the safe setup and usage of the ammeter. □ Place an ammeter to measure currents in a parallel circuit. □ Measure total and individual currents in a parallel circuit.

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