EET-117_LAB 5 23W

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Centennial College *

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117

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Electrical Engineering

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Apr 3, 2024

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Centennial College ELECTRICAL ENGINEERING TECHNICIAN & TECHNOLOGY Course: EET-117 Name Nevardo Williams Student Number 301307103 Date February 16, 2024 Lab #5 OHM'S LAW & POWER IN DC CIRCUITS Based on Experiments in Basic Circuits by David Buchla Objectives: 1. Measure and plot the current-voltage relationship for a resistor. 2. Given a graph of current-voltage for a resistor, determine the resistance. 3. Find the power in a resistor using each of the three basic power equations. 4. Indirectly measure the power in a variable resistor at various settings of resistance. 5. Plot the power dissipated as a function of resistance for the variable resistor of objective 5. Required Instruments and Components: DMM (Digital Multi-meter) Power supply Alligator test leads (from the EET-117 lab kit) Resistors: 330 Ω, 1.0 kΩ, 2.2 kΩ (from the EET-117 labkit) Potentiometer of any value (from the EET-117 lab kit example: when it is labelled 102 it is – 10x10 2 Ohm or 1 kOhm resistor) Page 1 of 6

Procedure 1. Obtain resistors listed in Table 1. Measure each resistor and record the measured value in Table 1. A reminder of steps to measure resistance using lab DMM (a reference to the manual): 1. Connect the device under test to the instrument, as shown: 2. Select a resistance measurement function: • Press 2 to select 2-wire ohms. Ω Table 1. Measured resistance values (3 significant digits, metric prefixes) Component Listed Value Measured Value Marks R 1 330 Ω 0.326 /2 R 2 1.0 kΩ 0.993 /2 R 3 2.2 kΩ 2.17 /2 2. Connect R1 into the circuit shown in Figure 1 . Caution! An ammeter can be easily damaged if it is incorrectly connected. Have your instructor check your connections before applying power. Fig. 1 3. Adjust the power supply for a voltage of 2.0 V. Measure the current and record it in Table 2 . Table 2. Measured current values (3 significant digits, metric prefixes) V s 2.0 V 4.0 V 6.0 V 8.0 V 10.0 V Marks I 6.06 mA 12.1 mA 18 .1 mA 24.2 mA 30.3 mA /5 4. Adjust the power supply for 4.0 V and measure the current. Record the current in Table 2 . Continue taking current readings for each of the voltages listed in Table 2 . 5. Replace R1 with R2 and repeat steps 3 and 4. Record the data in Table 3 . Table 3. Measured current values (3 significant digits, metric prefixes) V s 2.0 V 4.0 V 6.0 V 8.0 V 10.0 V Marks I 2 mA 4 mA 6 mA 8mA 10mA /5 6. Replace R2 with R3 and repeat steps 3 and 4. Record the data in Table 4 . Page 2 of 6

Table 4. Measured current values (3 significant digits, metric prefixes) V s 2.0 V 4.0 V 6.0 V 8.0 V 10.0 V Marks I 9.09 uA 1.81 mA 2.72 mA 3.63 mA 4.54 mA /5 7. On Plot 1 , graph all three I-V curves using the data from Tables 2, 3, and 4 . Plot the dependent variable (current) on the y-axis and the independent variable (voltage) on the x-axis. Choose a scale for the graph that spreads the data over the entire grid. Label the three resistance curves with the resistor value. TIP : you can use MS Excel to create the graph as was shown in previous Lab Plot 1 Marks: / 15 8. Construct the circuit shown in Figure 2 . The ammeter is connected in series. Ask the instructor to check your circuit before applying power if you are not sure of the connections . Fig. 2 Page 3 of 6

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9. Using your DMM, set the power supply voltage to 12.0V. This voltage also appears across R1, (ignoring the very small v oltage drop across the ammeter). Record the voltage and current (in mA) in the top portion of Table 5 . Table 5. Measured and calculated values (3 significant digits, metric prefixes) Measured value of Marks Resistance Voltage Current kΩ V mA /3 Computed Power P = IV P= I 2 R P = V 2 /R mW mW mW /6 10. Using the measured resistance, voltage and current, compute the power dissipated in R1 . Use each of the three forms of the power law and enter your results in the bottom portion of Table 5 . You should find reasonable agreement between the three methods. Determining Power in a Variable Resistance 11. Modify the circuit by removing the ammeter and adding a 1 KΩ potentiometer in series with R1, as shown in Figure 3 . R2 is the 1 KΩ potentiometer (connected as a rheostat). Fig. 3 Connect the center (variable) terminal to one of the o76t777777777777776t766t76utside terminals. Use this and the remaining terminal as a variable resistor . Adjust the potentiometer to 100 Ω. (Always remove the power source when measuring resistance) . 12. Measure the voltage across R1 and the voltage across R2. Enter the measured voltages in Table 6 . As a check, make sure that the sum of V1 plus V2 is equal to 12.0 V. Then compute the power dissipated in R2 using the equation: Page 4 of 6

Table 6. Measured and calculated values (3 significant digits, metric prefixes) Variable Resistance Setting (R 2 ) V 1 (measured) V 2 (measured) Power in R 2 : P 2 = V 2 2 R 2 Marks 100 Ω /4 200 Ω /4 330 Ω /4 800 Ω /4 1 kΩ /4 Total: /20 13. Disconnect the power supply and set R2 to the next value shown in Table 6 . Reconnect the power supply and repeat the measurements made in step 12. Continue in this manner for each of the resistance settings shown in Table 6 . 14. Using the data in Table 6 , graph the relationship of the power, P 2 as a function of resistance R 2 on Plot 2 . Since resistance is the independent variable, plot it along the x-axis and plot power along the y-axis. An implied data point can be plotted at the origin because there can be no power dissipated in R 2 without resistance. A smooth curve can then be drawn to the origin. Plot 2 Page 5 of 6

Marks: / 10 Conclusions. The conclusion summarizes the important points of the laboratory work. You must analyze the examples to add emphasis to significant points. You must also include features and/or things you have done /benefits of a particular procedure, instrument, component, or circuit directly related to the experiment . Marks: / 20 Rubric-Grading Criteria Max. Marks Punctuality 10 Lab Safety 20 Procedure 75 Conclusion 20 Neatness, Spelling, Grammar, and Sentence Structure 10 Total: /135 Page 6 of 6

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