Chapter 6 Electromechan e r m m c a a ni cal a S Sy s st ems e s 155 5 Copyright Goodheart-Willcox Co., Inc. Copyright Goodheart-Willcox Co., Inc. 11. Close the SPST switch and slowly adjust the power supply from zero until the plunger of the solenoid is drawn into the core. Record the current necessary to pull the plunger. 12. Open the SPST switch adjust the power supply to the voltage indicated in Step 8. 13. Open and close the SPST switch several times. Describe what happens. 14. Disconnect the circuit and return all components to the storage area. Analysis 1. What is a solenoid? 2. Where are solenoids used? 3. Why are solenoids sometimes called pusher coils? 4. Why are solenoid plungers spring-loaded?