1. The larger contactor sizes are used to provide remote control of relatively high-current circuits where it is too
expensive to run the power leads to the remote controlling location.
a. True
b. False
2. AccordingtoFleming’slefthandrule,motoractionwilltendtoforcetheconductorinadownwarddirection.
a. True
b. False
3. The function of the blowout magnet is to move the arc downward at the same time that the contacts are opening.
a. True
b. False
4. A mechanically held or latching relay is operated by electromagnets.
a. True
b. False
5. Mechanically held relays are often used in machine tool control circuits.
a. True
b. False
Name: Class: Date:
Unit 8 Contactors
6. Time clocks and photo cells are generally ____.
a. used to control AC motors b. provided to monitor the contactors
c. provided for overload protection d. used for lighting loads
7. An arc-quenching device is used to ensure ____.
a. better extinguishing action b. better contact
c. longer contact life d. more power
8. With ____, the blowout coil magnetic field and the conductor (arc) magnetic field will reverse simultaneously.
a. AC polarity b. AC current
c. DC polarity d. DC current
9. Most operating coils are ____ by contacts to prevent an accidental coil burnout.
a. disconnected automatically b. monitored regularly
c. connected intermittently d. normally disconnected
10. Generally, mechanically held relays are available in 10- and ____-ampere sizes.
a. 12 b. 15
c. 20 d. 24
Name: Class: Date:
Unit 8 Contactors