EETQ 114 Lab 3 - Series Circuits

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Centennial College *

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EETQ114

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Electrical Engineering

Date

Jan 9, 2024

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pdf

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Page 1 of 4 Centennial College Electrical Engineering Technician / Technology EETQ-114 Electronics 1 and Instrumentation 1 Name: Student #: Section: Date: LAB #3 Series Circuits Objectives: • Use Ohm's law to find the current and voltages in a series circuit. • Apply Kirchhoff's voltage law to a series circuit. Theory: The current in a resistor is directly proportional to the voltage across the resistor as stated by Ohm's law. Consider the simple circuit illustrated in Figure A . The source voltage is the total current multiplied by the total resistance. This can be stated in equation form as: 𝑉 ? = 𝐼 ? 𝑅 ? Figure A Figure B In a series circuit, the circuit elements are connected together with only one path for current. Figure B illustrates a series circuit with two resistors. When we join resistors in series, the total resistance is the sum of the individual resistors. The total resistance for the circuit in Figure B is: 𝑅 ? = 𝑅 1 + 𝑅 2 Substituting this equation into Ohm's law gives: 𝑉 ? = 𝐼 ? (𝑅 1 + 𝑅 2 ) Multiplying both terms by IT results in: 𝑉 ? = 𝐼 ? 𝑅 1 + 𝐼 ? 𝑅 2

Page 2 of 4 The identical current, IT, must flow through each resistor. This causes a voltage drop across each resistor, which can be expressed as: 𝑉 ? = 𝐼 ? (𝑅 1 + 𝑅 2 ) This result illustrates that the source voltage is equal to the sum of the voltage drops across the resistors. This relationship illustrates Kirchhoff's voltage law, which is more precisely stated as: “ The algebraic sum of all voltage rises and drops around any single closed path in a circuit is equal to zero . ” It is important to pay attention to the polarity of the voltages. Current from the source creates a voltage drop across the load. The voltage drop across the load will have an opposite polarity to the source voltage, as illustrated in Figure B . We may apply Kirchhoff's voltage law by using the following rules: 1. Choose an arbitrary starting point. Go either clockwise or counterclockwise from the starting point. 2. For each voltage source or load, write down the first sign you see and the magnitude of the voltage. 3. When you arrive at the starting point, equate the algebraic sum of the voltages to zero. Equipment: • Breadboard • Variable DC Power Supply (BK Precision 1672) • Alligator test leads • DMM (Keithley 2110) • Resistors: 47 Ω, 100 Ω, 270 Ω, and 330 Ω Procedure: 1. On your breadboard, build the circuit illustrated in Figure 1 . Connect the resistors in series. 2. Using the colour coded values of resistance, determine the total resistance of the circuit. Calculated Total Circuit Resistance = ___________________ Ω 3. With the power supply still OFF and disconnected from the circuit, measure the total resistance of the circuit between the input leads ( Figure 2 ). Measured Total Circuit Resistance = ___________________ Ω 5 Figure 1 Figure 2 – R T measurement 4. Using the measured total resistance value from Step 3, determine the current that would be flowing through the circuit if the supply voltage (V S ) is 10 v . Calculated Current Flow = ___________________ A 5. Complete the circuit shown in Figure 3 , making sure that the DMM is in the voltmeter setting. Turn ON the Power Supply and set the supply voltage (V S ) to 10 V .

Page 3 of 4 Figure 3 Figure 4 - voltage measurements on R 1 6. Set the negative lead of your Voltmeter on E , and measure the voltages between the following points (Refer to Figure 4 ). a) A and E V AE = V A = ___________ volts b) B and E V BE = V B = ___________ volts c) C and E V CE = V C = ___________ volts d) D and E V DE = V D = ___________ volts e) E and E V EE = V E = ___________ volts 7. Measure the voltage drop on R 1 by placing the leads across Resistor 1. V R1 = _____________ V 8. Compare the above value with the difference between V A and V B (V AB ). V A – V B = ________________ V. Are they approximately the same? ( yes / no ) 9. Measure the voltage drop on R 2 . V R2 = _____________ V 10. Compare the above value with the difference between V B and V C (V BC ). V B – V C = ________________ V. Are they approximately the same? ( yes / no ) 11. Measure the voltage drop on R 3 . V R3 = _____________ V 12. Compare the above value with the difference between V C and V D (V CD ). V C – V D = ________________ V. Are they approximately the same? ( yes / no ) 13. Measure the voltage drop on R 4 . V R4 = _____________ V 14. Compare the above value with the difference between V D and V E (V DE ). V D – V E = ________________ V. Are they approximately the same? ( yes / no ) 15. What would be the result of any of the measurements if the voltmeter is connected backwards?

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Page 4 of 4 16. Now turn OFF the Power Supply and connect the ammeter at point A in the circuit. Please make certain that the ammeter is connected in series otherwise, damage to the meter may result. Before applying power, have your instructor check your circuit. 17. Turn the Power Supply ON and record your reading I A in the table below. Ammeter position Ammeter Reading (mA) A B C D E 18. Repeat the procedure moving the ammeter to points B , C , D , and E in the circuit, remember to turn OFF the power supply before making any changes and to complete the circuit where you have removed the ammeter. Conclusion: State briefly, but clearly, what you have gained from this assignment. Lab Submission: - Please submit this lab report at the beginning of the next lab class for a full grade. Criteria Max Grade Materials, Tools and Equipment Set-up 1.5 Following Procedure 2 Data Collection and Analysis 2 Evaluation of Experiment, Review Questions 2 Conclusion 1.5 Spelling, Grammar, Sentence Structure 1 TOTAL