Test your basic knowledge |

Subjects : science, engineering
Instructions:
  • Answer 50 questions in 15 minutes.
  • If you are not ready to take this test, you can study here.
  • Match each statement with the correct term.
  • Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.
1. Alternating current may be defined as...






2. Why is 440-volt - three-phase power more commonly used in mining than 220-volt - three-phase power?






3. What position of a selector switch using a voltmeter would you select to check a 120-volt AC circuit to obtain the most accurate reading?






4. A control power transformer...






5. The speed of an alternating current - squirrel-cage induction motor is...






6. If 13 -200 volts are measured from phase-to-phase across a wye-connected secondary - What is the phase-to-ground voltage?






7. What value of voltage will be measured from phase-to-phase - in a wye-connected secondary - if 2 -300 volts is measured from phase-to-ground?






8. The purpose of a zig-zag transformer is to...






9. Using a 10:1 ratio transformer - the terminals on the secondary side or lower voltage side would be marked...






10. The transformer used only to measure voltage is a...






11. Not true about AC power?






12. When connecting 3 single-phase transformers into a three-phase system - which of the following is NOT required for the single-phase transformers.






13. A transformer has 2000 turns in the primary and 500 turns in the secondary. The primary voltage is 3 -200 volts. What is the secondary voltage?






14. Current transformers - or CT's - are used to...






15. Where should grounding resistors be located?






16. AC voltage is raised or lowered by means of...






17. High voltage is used to transmit power over long distances...






18. Not a symptom of electrical shock?.






19. Compared to the secondary of a loaded - step-down transformer - the primary has...






20. Compared to the secondary of a loaded - step-down transformer - the primary has...






21. A wound-rotor induction motor has all the following EXCEPT...






22. The neutral ground-bed electrical power system of an underground mine should be separated from the lightning arrestor grounds by at least...






23. Not an acceptable method for the installations of surface transformers?






24. Which of the following is not needed when using an ohmmeter to determine if a motor is grounded?






25. Surface transformer installations - unless constructed to eliminate shock hazards - must be installed at least...






26. Two 10-hp induction motors are operating on 460 volts AC. One motor is connected by single- phase; the other is connected in three-phase. The three-phase will...






27. If the conductors of a balanced - three-phase circuit pass through a current transformer - how many amps will flow in the transformer?






28. What happens to a motor that is connected to a three-phase cable when two of the cable's leads are reversed?






29. A 3-phase - 2 speed - constant torque motor is running at fast speed. The motor windings are connected wye for fast speed. Motor leads T4 - T5 and T6 are connected to the line leads. Motor leads T1 - T2 and T3 should be...






30. The minimum allowable size for trailing cables for mobile haulage equipment powered by alternating current is...






31. If 2000 watts is read in the primary of a single-phase transformer - What is the wattage in the secondary? (Assuming no losses.)






32. What is a capacitor?






33. What is the danger when working around capacitors?






34. If any two-phase wires are reversed on a three-phase motor - the motor will...






35. A transformer has a primary voltage of 2 -800 volts and a secondary reading of 140 volts. If there are 2000 turns on the primary - how many turns are on the secondary?






36. A transformer with a 1:1 ratio is usually a (an)...






37. When troubleshooting a circuit with a bank of capacitors - what precautions must be taken?






38. Three-phase AC underground cables must be provided with overcurrent protection using a...






39. A solenoid coil is...






40. A transformer has 1 -600 turns in the primary and 400 turns in the secondary. The primary voltage is 2 -400 volts. What is the secondary voltage?






41. The load to which the secondary winding of a current transformer was connected has opened. The secondary leads should be...






42. The primary function of a power transformer is to provide...






43. A burn causing a blister is classified as a...






44. Under fault conditions - the grounding resistor in a high voltage circuit limits the voltage drop in the grounding circuit external to the resistor to not more than...






45. Should a ground fault occur - what device can be installed to limit the current in the neutral of a three-phase AC system?






46. The standard frequency of alternating current used at a mine is...






47. The property of an electrical circuit that opposes any change in voltage is called...






48. Define alternating current...






49. Current in an AC circuit may be measured by...






50. How do you change the direction of a 3-phase AC motor?