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. Transformer losses are classified as _____ and _____.






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






3. The output rating of a transformer is based upon the maximum _____ the transformer is capable of carrying without exceeding a certain temperature rise.






4. 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






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






6. Copper loss is known as _____ loss.






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






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






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






10. The loss of power required to reverse the core magnatism each time the current reverses. This loss is caused by friction between the molecules of iron as these particles are aligned first in one direction and the in the opposite direct as current dir






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






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






13. 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.






14. A partial or total local failure in the insulation or continuity of a conductor.






15. 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.






16. 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.






17. 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.






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






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






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






21. The voltage induced in the coil is directly proportional to this






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






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






24. How coercivity is minimized






25. 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






26. 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






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






28. A single electrical circuit.






29. The formula for the voltage related to turns ratio






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






32. Divergence of the magnetic field causes this






33. How the voltage and the number of turns are related for the voltage related to turn ratio






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






35. This is the most advanced and most efficient type of tansformer; it is commonly used in x-ray equipment






36. With no load on the secondary winding - a small current flows in the primary called _____ _____.






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






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






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






40. A transformer loses less than _% in energy






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






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






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






44. 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






45. What does transformer efficiency mean?






46. A large amount of power wasted with the open-ended core






47. Reference to a jumper or conductor - to or from a piece of electrical equipment.






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






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






50. The formula for the current related to voltage law