Electrical Mechanic/Test Technician Study Guide Test.

Electrical Mechanic/Test Technician Study Guide Test. 1. Voltage an electromotive force or potential ditterence expressed in volts. Potential to do work. 2. Direct Current (DC) Electric current that flows in only one direction 3. Alternating Current (AC) A flow of electric charge that regularly reverses its direc- tion. Bidirectional. 4. Wattage the electrical power consumed by a device. 5. Coulomb the SI unit of electric charge, equal to the quantity of electricity conveyed in one second by a current of one ampere. 6. 1 amp = 1 coulomb/sec 1 amp = 6.25 x 10 (18) 7. Ohm unit of electrical resistance 8. Ampere (amp) Unit that measures the strength of an electric current. 9. Ammeter a device used to measure current in amperes. 10. Voltmeter a device used to measure electrical potential or voltage. 11. Wattmeter Measures electric power in watts 12. Megger An instrument used for checking the insulation resis- tance on motors, feeders, bus bar systems, grounds, and branch circuit wiring. Read in millions of ohms. 13. Oscilloscope a device used to display the shape of an electrical wave. 14. Multimeter A measuring instrument for current, voltage, and resis- tance. 15. Frequency meter Used to measure the frequency of an AC signal. 16. micrometer A gauge which measures small distances or thicknesses. 17. vernier caliper instrument used for measuring precise linear dimen- sions 18. Wire gauge A standard measure of the diameter or thickness of a strand of wire 19. Ohmeter a device used to measure resistance 20. Architect's Scale A specialized ruler used in making or measuring re- duced scale drawings. It is marked with a range of cal- ibrated ratios used for laying out distances, with scales indicating feet, inches, and fractions of inches. Used on drawings other than site plans. 21. Planimeter Engineering tool designed to measure distance as its pointer is traced around a pattern. 22. Of the following electrical devices, C. Transformer the one that is NOT normally used Transformers do not use direct current (DC). Transform- in direct current electrical circuits is a .... A. Circuit breaker B. Double-pole switch C. Transformer D. Inverter 23. Of the following motors, the one ers work on alternating current (AC), which is electrical current that flows in a single direction. A transformer's principle is based on electromagnetic induction, which requires a voltage source that changes with time. A DC supply is unidirectional, so the transformer cannot work. If the input terminals of a transformer are connected to a DC voltage, the transformer usually burns. C. Squirrel cage induction. Cheap and easy to install - that does NOT have brushes is the squirrel cage induction motors do not contain brushes, motor. slip rings, commutators, permanent magnets, position A. DC shunt B. DC series C. Squirrel cage induction D. Compound 24. Of the following materials, the one that is COMMONLY used as an electric heating element in an electric heater is... A. Zinc B. Brass C. Terne plate D. Nichrome sensors, or other components that increase their overall cost. Their simple construction ensures they are gener- ally easy to install and maintain. D. Nichrome. Most heating elements use Nichrome 80/20, which is 80% nickel and 20% chromium. Nichrome is ideal because it has high resistance and forms a chromium oxide layer when heated for the first time. 25. A bolt is specified as 1/4-28 means Bolt is 1/4 inch in diameter and has 28 threads per inch the... 26. Name 3 basic components of the atom: 27. Two opposing forces hold the electron in place. They are force and attraction. Proton, neutron, electron Centrifugal force & electrical attraction 28. electromotive force (emf) Electrons can be moved from one atom to another by applying some form of or pressure. 29. Amperage (amps) The measurement of the amount of electricity flowing past a given point in a conductor per second (i.e., cur- rent).