Test your basic knowledge |

Transformers

Subject : 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. Provides the ratio between the applied primary voltage and the induced secondary voltage as result of the turns ratio






2. A system of conductors in which at least one conductors or point (usually the middle wire or neutral point of a transformer or generator windings) is intentionally grounded either solididly or through a current-limiting device.






3. The winding to which voltage is supplied is called the _____ winding.






4. If the transformer is used as a _____ transformer - the high voltage winding is the primary.






5. Connected to earth or to some conducting body which serves in place of the earth.






6. Core losses are _____ loss and _____ - _____ loss.






7. What does transformer efficiency mean?






8. Insulated primary and secondary coils are in close proximity to each other - no iron core and very innefficient






9. The input side that attaches to the AC supply it recieves the electrical energy or incoming voltage






10. In a transformer the _____ current will always flow in such a direction that its magnetizing action will oppose the magnetizing action of the primary winding.






11. How a variable degree of core saturation is accomplished in a saturable reactor?






12. A stationary device for transferring alternating current electrical energy from one circuit to another circuit by electromagnetic means.






13. Instrument transformers reduce high voltages and currents to safe - usable values for the operation of _____ _____.






14. To prevent injury to personnel when servicing any equipment connected to a current transformer - the secondary winding must be ____ - _____.






15. This core is more efficient than the air core because the iron core in each coil intensifies the magnetic flux in both primary and secondary coils when they become magnetized as current flows through each set of coils






16. The shape of the core of the transformer ensures a ______________ for the magnetic flux with maximum concentration within the core and minimum leakage of the air






17. Autotransformers are not safe when they supply a _____ voltage from a high voltage source.






18. The turns ratio between the windings (primary & secondary) of a transformer unless otherwise specified.






19. A test instrument used to indicate low voltage potentials in the range of 110 to 600 volts either alternating or direct current. (slang term: wiggy)






20. _____ shows that the voltages across the windings of a transformer are directly proportional to the turns in each winding.






21. Determines if the transformer is a step up or step down transformer






22. The output which can be delivered for the time specified at rated secondary voltage and rated frequency without exceeding the specified temperature limitations.






23. The terminals of the high voltage winding are marked _____.






24. How coils serve as the primary and secondary windings for an autotransformer






25. It refers to the direction of current flow in a closed circuit.






26. The magnetic lines of force that flow from the north pole of a magnet and return to the south pole.






27. The turns of both windings are cut by the same flux; therefore the induced emf in each turn of both windings is the _____.






28. The characteristic that requires energy to carry out the constant reorientation of the magnetic dipoles in the hysteresis loss






29. Divergence of the magnetic field causes this






30. The current related to turns ratio law






31. The capacity of a transformer is rated in ____ _____.






32. When an alternating current is applied to the high-voltage (H) winding of a transformer with no load on the secondary (X) winding - a small current - called the _____ current - flows in the primary.






33. Copper loss is known as _____ loss.






34. Hysteresis Loss can be reduced by using a core with this feature






35. A transformer primary (H) that has 400 turns is wound to step the voltage down from 240 volts to 120 volts. The number or turns (TX) required in the secondary (X) winding is _____.






36. A transformer loses less than _% in energy






37. If the transformer is used as a _____ transformer - the low voltage winding is the primary.






38. _____ currents are reduced by laminating the core.






39. The relationship between current and voltage in the coils are inverse






40. Defined as the ratio of the power output to the power input (in a closed circuit containing resistance)






41. Modern; extremely efficient-more effective coupling between primary and secondary coils; smaller and lighter






42. A choke coil uses this to induce current






43. 3 types of transformers






44. The formula for the current related to voltage law






45. An electromagnetic device that operates on the principle of self induction. It uses AC.






46. Current flows through the primary winding in response to primary voltage and sets up a magnetic field that varies in direction and stregnth. under the influence of the changing magnetic field an AC voltage/kv is induced across the secondary coil by e






47. Transformers with 4800 volt primaries and 120/240 volt secondaries - either pole or subway type - with two secondary windings terminating at internal links which provide for parallel operation of the secondary windings at 120 volts or series operatio






48. The current flowing through the primary winding - in response to the applied primary voltage - sets this up






49. A magnetic field changing with respect to the conductor will generate a _____ in the conductor.






50. A transformer which when supplied from a constant potential source automatically maintans a constant current in its secondary circuit under varying conditions of load impedance. Used on series street light circuits.