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 is a continuously adjustable Autotransformer.






2. Used to increase the magnetic flux in a transformer






3. A variable transformer is a continuously adjustable _____ - has the primary winding and secondary winding electrically connected.






4. Anything above 600 volts is _____?






5. The number of turns can be adjusted in these types of transformers






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






7. The terminals of the low voltage winding are marked _____.






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






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






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






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






12. The total numbre of lines or force issuing from a pole. (north or south)






13. Divergence of the magnetic field causes this






14. 3 types of transformers






15. An instrument used to measure electrical current.






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






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






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






19. 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 _____.






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






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






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






23. What does transformer efficiency mean?






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






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






26. This type of core is moderately efficient due to closing the core and layering design which reduces power loss from less leakage flux which provides a continuous path for magnetic flux and an increase in field strength






27. 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.






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






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






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






31. 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






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






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






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






35. The formula for the current related to voltage law






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






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






38. 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.






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






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






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






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






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






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






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






46. For a step up and step down transformer if the turns ratio is constant this is the only way to change the output voltage






47. 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.






48. _____ currents are reduced by laminating the core.






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






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