194 Copyright Goodheart-Willcox Co., Inc. 9. Turn on the switch. The three bulbs should be on. Measure the current with the inductive clamp. Remember to use only one wire. The hot wire between the switch and TP2 is a good choice. The neutral wire may be used but ensure it is common to all three bulbs. Check the accuracy for current as in Step 7 and record tolerance. 10. Turn off the bulbs. 11. Measure the resistor value and check your accuracy as in Step 7 and record. 12. With the board still plugged in and the switch in the off position, check voltage between TP1 and TP2 and record value. 13. Leave the meter connected to TP1 and TP2 (use alligator clips or have a lab partner). Use a second meter and measure voltage between TP3 (which is same point as TP2) and TP4. Record the value. 14. Remove any two bulbs and repeat Steps 11 and 12. Record the new values. 15. Remove the last bulb and measure the voltage between TP1 and TP2. Record value. 16. Replace all bulbs and turn the switch on. 17. Measure the voltage between TP1 and TP2. Record the value. 18. Measure the voltage between TP3 and TP4. Record the value. 19. Turn off the switch, and allow the bulbs to cool down about three minutes. 20. Set up the meter to measure inrush (LRA) current. Place the wire in clamp jaw. 21. Turn on the switch. Record the inrush current. Incandescent bulbs draw a more current initially due to the cold filament. Note: the current may be too small for some meters to capture. (This will be performed with a motor in Chapter 13, Electric Motors.) 22. Leave the lab board wired for use in Lab 10.3. Lab Questions Use your digital multimeter or other electrical instruments to answer the following questions. 1. What is the source voltage? ______________________________________________________________________________________________________________ 2. What is the actual voltage range (tolerance) for Step 8? ______________________________________________________________________________________________________________ 3. What is the actual current range (tolerance) for Step 9? ______________________________________________________________________________________________________________ 4. What is the actual resistance range for Step 11 (tolerance)? ______________________________________________________________________________________________________________ 5. What is the voltage between TP1 and TP2 with switch off? ______________________________________________________________________________________________________________ 6. Explain the measured value? ______________________________________________________________________________________________________________ 7. Explain the measured value between TP3 and TP4 in Step 12? ______________________________________________________________________________________________________________