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. Find the turns ratio of a single-phase transformer with the following values: Primary power of 5KW - secondary current of 100 amps - and primary voltage of 250 volts.






2. 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?






3. What type of 3-phase AC motor is used most often around a mine?






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






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






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






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






8. Alternating current may be defined as...






9. 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?






10. All transformers step voltage up or down by...






11. 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...






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






13. The property of an electric circuit that opposes any change in current is called...






14. 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?






15. Not true about AC power?






16. The main function of CT's and PT's on a main substation is to...






17. When not connected to a load - the secondary leads of a current transformer should be...






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






19. Find the turns ratio of a single-phase transformer with the following values: Primary power of 10 KW - secondary current of 200 amps - and primary voltage of 250 volts.






20. What type motor is a wound-rotor induction motor?






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






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






23. 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...






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






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






26. A control power transformer...






27. Where should grounding resistors be located?






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






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






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






31. A transformer with 3000 turns in the primary winding has a primary voltage of 4 -800 volts and a secondary voltage of 240 volts. How many turns are in the secondary winding?






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






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






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






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






36. 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?






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






38. A solenoid coil is...






39. Define alternating current...






40. The size of a transformer is measured in...






41. The primary leads of a single-phase transformer should be connected to the...






42. Not a symptom of electrical shock?.






43. A transformer has a primary voltage of 2 -400 volts and a secondary reading of 120 volts. If there are 1 -500 turns on the primary - how many turns are on the secondary?






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






45. A current transformer has a ratio of 350:5. If the phase current is 70 amperes - what would be the secondary current?






46. The current on the primary side of a step-down transformer with a 4:1 ratio will be...






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






48. The secondary windings on a 10:1 step-down transformer will have a wire size...






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






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