# solution

26 Chapter 2 Symbols and Schematic Diagrams Review Questions 1. The symbol shown is a a. Polarized capacitor b. Normally closed switch c. Normally open held closed switch d. Normally open contact 2. The symbol shown is a a. Normally closed float switch. b. Normally open held closed float switch c. Normally open loat switch d. Normally closed held open float switch 3. The symbol shown is ank a. Iron core transformer 7. Referring to the circuit in Figure 2-20, should the float switch be connected as a normally open or normally closed switch? 8 Referring to the circuit in Figure 2-20, what circuit component controls the actions of the two CR contacts? 9. Why is a circle most often used to represent a coil in a motor control schematic? 10. When reading a schematic diagram. are the con- trol components shown as they should be when the machine is turned off or de-energized, or are they shown as they should be when the machine is in operation? b. Auto transformer c. Current transformer 11. Push-pull buttons are generally used because: a they are smalker in size than standard pash buttons b. they contain larger contacts that can withstand more curremt than standard push buttons c. they can perform more than one function while only requiring the space of one single-function push button d. They are larger in size than standard push but tons making them more visible to an operator d. Air core transformer 4. The symbol shown is a a. Normally open pressure switch. b. Normally open flow swisch. c. Normally open float switch d. Normally open temperature switch. 5. The symbol shown is a HOA 12. What device is gemerally used by lighted push buttons to reduce the voltage applied to the lamp? a. Series resistor. b. Transformer c. Series capacitor d. Series indactor. C C a. Double acting push button. b. Two-position selector switch. c. Three-position selector switch d. Maintained contact push button. 6 If you were installing the circuit in Figure 2-20 what type of push button would you use for the silence button? a. Normally closed. b. Normally open 13. How are components that are mechanically connected together generally identified on a schematic diagram? Review Questions 1. A single-phase 120 volt motor is controlled by a manual motor starter. The motor is not running and the switch handle on the starter is found to be 5. What is meant by the term “line voltage” on some pilot sensing devices? 6. Explain the difference between manual motor starters that provide low voltage release and those in the center position. What does this indicate? 2. Referring to the above question, what action is necessary to restart the motor and how is it accomplished? 3. A single-phase motor operates on 240 volts. Why should a starter that contains two load contacts be that do not. 7. What is the simplest way to determine if a motor is overloaded? 8. Refer to the circuit shown in Figure 3-7. What type of switch is connected in series with the motor, and is the switch normally open, normally closed, normally open held closed, or normally closed held open? used to control this motor? 4. A push-button manual starter has tripped on over load. Explain how to reset the starter so the motor can be restarted. 34 Chapter 3 Manual Starters 9. Refer to the circuit shown in Figure 3-10. When would the amber pilot light be turned on? a. When the manual-automatic switch is set in 10. Refer to the circuit shown in Figure 3-10. Is the float switch normally open, normally closed, nor- mally open held closed, or normally closed held open? the MAN. position. b. When the float switch contacts are closed. c. Anytime the manual starter is turned on d. Only when the manual-automatic switch is set in the MAN. position.

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