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. Define alternating current...






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






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






4. What should the duty rating of a grounding resistor be?






5. Which of the following does a squirrel cage induction motor have?






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






7. To protect against over-current in a three-phase circuit over-current protection must be provided for...






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






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






10. What steps up or steps down AC voltage?






11. Alternating current may be defined as...






12. 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.






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






14. A solenoid coil is...






15. The following motor leads are brought out of a 3-phase motor (T1 - T2 - T3 - T4 - T5 - T6). This motor is probably for...






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






17. 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?






18. 460 volts AC is required to operate two motors - one connected in single-phase and the other connected in three-phase. The three-phase motor will...






19. A control power transformer...






20. 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?






21. How should clothing be removed from a burn?






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






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






24. If a voltmeter were placed between two phase leads of a three-phase 480-volt system - the meter would read...






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






26. Not true about AC power?






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






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






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






30. What is the first step to be followed in aiding a victim of electrical shock?






31. What is a capacitor?






32. 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?






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






34. If a voltmeter is connected between a phase lead and the ground of a three-phase 480-volt system - the meter will read...






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






36. 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?






37. What is the danger when working around capacitors?






38. Where should grounding resistors be located?






39. A transformer with 1 -500 turns in the primary winding has a primary voltage of 2 -400 volts and a secondary voltage of 120 volts. How many turns are in the secondary winding?






40. 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.






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






42. 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...






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






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






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






46. If current were flowing through a grounding resistor in a 440-volt - resistance-grounded system - this would probably be because...






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






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






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






50. 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...