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. 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.






2. The volt-amperes of the primary of a transformer is equal to the _____ - _____ output of the transformer.






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






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






5. What does transformer efficiency mean?






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






7. This type of transformer power loss is caused by the continually changing AC current movement which constantly magnetizes/demagnetizes/re-magnetizes






8. The output side it develops AC by electromagnetic mutual induction - Secondary voltage is induced in this coil






9. Divergence of the magnetic field causes this






10. A transformer is a device that either increases or decreases alternating current and voltage using this principle






11. A transformer rated at 500KVA and below used for voltage transformation on the distribuition system.






12. The winding of a transformer to which electrical energy is supplied.






13. Function of the dielectric oil






14. A part of a circuit made of a low melting point material so that it will melt and break the circuit when a specified current exceeded. Always the weakest point in the circuit.






15. Both the primary and secondary coils in a transformer are arranged around this






16. 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






17. The formula for the voltage related to turns ratio






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






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






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






22. 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.






23. Two coils wound on a closed iron core form a ________.






24. 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






25. The 3 principle components of a transformer






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






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






28. Some losses occur in all transformers. These losses are classified as copper losses and _____ losses.






29. Transformers designed for 4800 volt primary operation - but the secondaries are connected 240/480 volts. Winding ratio is 10:1






30. closed core with a top and bottom. It directs the magnetic field towards the primary and secondary coils and increases the field stregnth






31. A transformer loses less than _% in energy






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






33. both coils in this core are heavily insulated






34. _____ shows that the voltamperes of the primary of a transformer equal the voltamperes of the secondary of a transformer.






35. ___________ is often used in laminated cores - increases electrical resistance which decreases eddy currents






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






37. The energy is always transferred without a change in frequency - but usually with changes in _____ and _____.






38. A magnet made by winding a coil of wire around a soft iron core. Current passed through this winding produces magnetic lines of force in the coil.






39. An instrument used to measure electrical current.






40. The relationship between amperage flowing through the coils and the number of turns on individual coils is inverse






41. A designated limit of operating characteristics based on definite conditions.






42. What is a rotation meter?






43. A single electrical circuit.






44. Central magnetic core made of






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






46. The entire transformer is placed in a metal tank then immersed in ________.






47. A transformer is a device that has no moving parts and that transfers energy from one circuit to another by _____.






48. 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






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






50. Is concentrated in the metal core