ELET4143
Electrical Machines and Controls
Spring 2008
Electrical Engineering Technology
SUNY College of Technology, Alfred, NY
ELET 4143 Electrical Machines and Controls Spring Semester 2008
Lab 2. AC Measurements
Objective: To measure voltage, current and power in a 120 volt single phase circuit. Analyze the relationships between the
three variables. Investigate the characteristics of the incandescent light bulb. Compare different power meters.
Procedure:
WARNING: 120 volt AC can be hazardous. Be safety vigilant when making measurements. Work with one hand.
Have your partner watching and checking.
1.- Set up a circuit consisting of four incandescent light bulbs connected in parallel. Provide AC power to the bulbs through
a variable AC source. Choose a 40 Watt, 60 Watt, 75 Watt and 100 Watt light bulb as available.
2.- Draw a schematic of a parallel circuit consisting of four 120 VAC bulbs. Label the bulbs L1, L2, L3 and L4.
3.- Using Excel, make a table where the rows are labeled for each bulb, L1, L2, L3, L4 and the totals. The columns will
indicate the individual bulb data and measurements. Begin by measuring the DC resistance of each bulb using an
ohmmeter. Record the results in the table. Indicate the voltage and currents on the schematic.
4.- Set the variable AC source for 120 volts, rms. Measure the voltage, the total current, and the current through each bulb.
Record these measurements in the results table.
5.- Measure, using an analog wattmeter, the total power and power dissipated by for each bulb. Show the meter
connections on the schematic. Record the measurements in a table. Your schematic should show how the meter is
connected.
6.- Use a plug in Kill-a-watt meter to measure the total power. This meter should be inserted between the variable AC
source and the light bulbs. Record the results in the table. Record the information about the instruments you used to make
these measurements.
Calculations (should be included in the lab report):
1. Using only the analog voltage and current measurements, calculate the total and individual bulb powers.
2. Place the results in a table.
3. Compare this calculation with your measurements. Based on this comparison, do the bulbs present an active,
reactive or apparent power load ?
4. Sketch a sine wave cycle showing the instantaneous relationship of voltage, current and power for bulb #1 (L1).
5. Explain the relationship between the resistance of each bulb and E, I and P.
6. Do some research on incandescent light bulbs. Determine how the light efficiency is specified. Add an item to the
results table to compare the efficiency of the different wattage bulbs.
7. Why do most commercial buildings use fluorescent lights instead of incandescent bulbs for primary lighting ?.
Include data and references along with your answer.
Lab Report:
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Individual lab reports, same data. Mention the names of the team members.
Include all the drawings that were made and the data that was obtained during the lab period.
The Lab report should be written in a professional way. A computer will be used for all text, schematics and
tables. The calculations may be shown free hand. Be sure to respond to the questions and comments mentioned
above.
Alfred State College
Electrical Engineering Technology
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