UW EE 215 - Study Notes (2 pages)

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Study Notes



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Study Notes

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School:
University of Washington
Course:
Ee 215 - Fundamentals of Electrical Engineering
Fundamentals of Electrical Engineering Documents
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EE215 Laboratory 6 Page 1 Steady State Sinusoidal AC Due At recitation week of May 29 June 1 Objectives At the end of this lab you will be able to Measure AC and DC voltages Understand what happens when measuring AC voltages with a DC voltmeter and vice versa Give the range of variation in wall socket voltages Explain AC voltage and current readings in circuits with capacitors and inductors Remarks For safety reasons do NOT directly measure AC wall voltages Yes you can actually do this safely with your meter if you are very careful to set it to measure voltage and not current and make sure you only touch the insulated plastic parts of the probes and not the conducting metal bits But for this lab don t do it Materials and Supplies The new part for this lab is the 9VAC transformer or wall wart It converts from 120V AC to 9V AC with the same frequency It just plugs in to the wall Be careful not to short circuit the output leads Note that many wall warts that look like this include a diode in the case and do not output true AC This one does not have a diode Procedure 1 a 10 points Pick your favorite wall socket Plug the transformer into the wall socket Measure and record the voltage at the transformer output using the AC voltage and DC voltage settings on your multimeter Now measure and record the voltage of your 9V battery using the AC voltage and DC voltage settings Compare the readings and explain why each is what it is Hint DC measures average voltage AC filters out DC before measuring unless you have an expensive true RMS meter You do not need to buy one for this lab b 5 points Measure the AC transformer output voltage using the AC voltage setting of your multimeter at least three times a day for two days Try to get a measurement in the morning some time in the middle of the day lunch or if you get home around 5PM and again just before you go to sleep You must use the same wall socket for these measurements If you can do one day as a weekday and one as a weekend so much the better c 10 points Plot the measurements from part b Calculate how much they vary in percent from high to low Try to explain why they vary Procedure 2 a 5 points Build circuit 1 Note You do not appear to have a 26 2 K resistor in your parts kit Perhaps you can create a resistor combination with an equivalent resistance as close as possible to 26 2 K b 10 points Supply circuit 1 with your 9V battery and measure and record DC voltage across each resistor and the source Then supply it with the 9V AC from the transformer output you do NOT have to use the same wall socket as in Procedure 1 although you can if you want to and measure and record the AC voltage across each 30 vs 26 2K Circuit 1 R D Christie 5 22 01 EE215 Laboratory 6 Page 2 resistor and of the source Calculate the current using the voltage across the 30 resistor Allowing for the variation in source voltages are the measured voltages and currents about the same Why 30 c 5 points Build circuit 2 and repeat part b Explain why the AC and DC voltages and currents are different or why they are not d 5 points Compare the AC voltages and currents between circuit 1 and circuit 2 Do you expect them to be about the vs 0 1 F same or significantly different Explain why Are they what you expect They should be Circuit 2 Procedure 3 a 10 points Build circuit 3 Design an experiment i e plan 26 2 K what measurements to take to verify KVL for this circuit Perform the experiment Does KVL hold Explain why or why not b 5 points Build circuit 4 Measure and record the AC 0 1 F voltage across the inductor and resistor Use the voltage across 9VAC the resistor to determine current Calculate the expected voltage and current values using the measured value of the source voltage Do your calculations match your measurements Don t forget the internal resistance of the Circuit 3 inductor you found in Lab 5 c 5 points Add the 0 01 F capacitor in parallel with the inductor in circuit 4 Measure AC voltage across the resistor and calculate current Did current go up or down This change is small Why d 10 points Calculate the nominal impedance of each 100 component in the circuit you used in part c Calculate the magnitude and angle of the current supplied by the 9V transformer assuming the voltage has zero angle Explain whether your calculated result is consistent with your LJ 410 9VAC observations in part c 100mH Bring the circuit of part c to recitation 20 points Circuit 4 R D Christie 5 22 01


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