Introduction to Electrical Engineering
Only DC voltages, or constant voltages, were used in this lab. Current is the rate of flow of charge through an element and is measured in amperes. Lastly, resistance is a measurement of the force opposing a current through an element. Resistance Is measured In ohms, Q. Voltage, current, and resistance are all related In Ohms Law, a useful equation used repeatedly In the lab. Ohm’s Law states that voltage= current times resistance. The Clockwork voltage law Is also used In this lab. This law states that the sum of voltages through a closed loop is equal to zero.
Both Ohm’s Law and the Kerchief Olathe law are used to check measurements obtained in the lab and are very useful in circuit analysis. Ill. Materials and Equipment Regulated DC Power Supply, Model 3010 by R. S. R Electronics True ARMS Digital Millimeter Ammeter 1000 Q resistor ANT-102 Theorist Photoreceptor Potentiometer Adulteresses 2 mm pieces of magnet wire IV. Procedure A. Measuring DC Voltage With the millimeter set to measure DC voltage, red and black test wires were attached to the V Q Hz’s jack and the COM Jack on the front of the millimeter and then to the Jacks for +5 V and COM on the DC power supply.
The range on the millimeter as set to 20, and the power supply was turned on and adjusted to +6 V and -12 V. The two variable voltages were recorded, and then the total voltage in series was measured and recorded. 8. Measuring DC Current The millimeter was set to measure current, and the red wire was moved to the ma Jack. With the power supply off, a circuit was created with the 10000 resistor In series with the ammeter, so the current will flow from the source through the resistor before the ammeter (see Circuit 1 in Appendix).
The voltage source was set to V. Resistance was calculated with Ohm’s law. C. Measuring DC Resistance A circuit containing the DC power supply, resistor, millimeter, and ammeter was created (see Circuit 2 in Appendix). The voltage across the resistor and current through the resistor was measured and recorded for 5 different voltages, from approximately 1. Veto VI. This was repeated two more times, and all data was entered into Excel and graphed with an XX scatter and a trending for voltage vs.. Current. The actual resistance was calculated.
Next, connect the 10000 resistor to the V Q Hz’s and COM Jacks of the millimeter, switch the function to ohmmeter, and adjust the range. Measure and record the resistance recorded by the ohmmeter. D. Sensors A. Theorist A theorist was obtained and connected to the voltage source and millimeter. The resistance across the theorist was measured and recorded. Next, the theorist was held between two fingers and the resistance was measured and recorded. The two temperatures were calculated from the resistance. B. Photoreceptor The resistance of the photoreceptor was measured in normal light, and then while held inside of a hand.
These resistances were recorded. C. Penitentiaries The resistance between terminals A and B was measured and recorded, and then the resistances between terminals A & W and B & W were measured. The measurements for A & W and B & W were repeated 3 more times as the shaft of the potentiometer was rotated 90 degrees clockwise for each measurement. E. Audio Speakers Magnet wires, labeled A and B, were obtained, and their resistances were measured separately using the millimeter and subtracting the resistance of the test wires alone.
From the resistances, the AWG wire gauge of each of the wires was found from the table in the back of the lab handout (see lab handout, in Appendix). Next, the resistance of the audio speakers was determined from the ohmmeter and recorded. V. Results Voltage A +6. 031 v Voltage B 11. VI Voltage in series +17. 87 V The Kerchief voltage law states that the net voltage in a closed loop is zero. The voltage in series, +17. 87, represents the total difference in voltage from the two variable sources on the power supply. This creates a net voltage of zero for the loop. B.
Measuring DC Current Ohm’s Law: R=V/I R=5. 039 V/4. 95 RNA= 1018 Q (10 10,000 W dissipated If the small resistor can only withstand 1 W of power dissipation, then the small resistor will overheat and may burn out. C. Measuring DC Resistance R-4. 962 V/4. 91 RNA= 1. 010 k See attached sheet for data and voltage vs.. Rent graphs for three trials. This resistance differs slightly from the resistance calculated from Ohm’s Law, above. This is likely because the current measured above is slightly lower than the actual current because the small resistor in the ammeter is not ideal.
Both values, however, are still in the range В±5% range of the resistor, 950 Q to 1050 Q. D. Sensors a. Theorist 1000 Q + -43 Orca Room temp: 1. 2149 1000 Q + -43 20. 0 c warm temp: . 9874 1000 Q + -43 25. 3 c b. Photoreceptor A photoreceptor could be used in streetlights to sense darkness by the increase in resistance over a circuit exposed to the sky. A resistance threshold could be used to then power the streetlights to turn on, and then turn off when the resistance drops again in the morning. C.
The graphs generated from the data were expected to fit the equation for the 1000 k resistor. The actual equations were Fl . Xx+. 107, Fl . Xx+. 133, and Fl . Xx+. 106, all very close to the equation EX. In part D, the three sensors used produced varying values of resistance based on temperature, light intensity, and position. The theorist was used to calculate values for room temperature and for the temperature between two fingers: ICC and 25 C. Although he actual temperature values are unknown, these results are reasonable and can be considered accurate.
Lastly, in part E, the wire gauge of magnet wire was calculated. There was significant error in this measurement, as the first calculation gave a value of 70 Q/km, which does not correspond to a wire gauge on Table I in the lab handout (see Appendix). This value was in between the values for 22 and 24 AWG, 51. 7 Q/km and 87. 5 Q/km. This error can likely be explained by the fact that the wires were not accurately measured to 1 meter. The actual AWG values for the two wires are not now, but the calculated wire gauges are probably not correct.
If this lab were repeated, both strands of magnet wire would be carefully measured to 1 meter. Failure to accurately measure the magnet wires in part E was the only major error in connecting the test wires correctly. The diagrams provided in the lab handout were very helpful. All sections of the lab were completed successfully and all concepts were well understood, and all other results obtained in this lab may be considered accurate and reliable. This lab provided an appropriate introduction to the basic electrical concepts that will be used in the classroom.
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