Friday
October 24, 2014

Homework Help: electronics technician

Posted by mompati on Tuesday, June 18, 2013 at 10:26am.

19. In a solenoid, where is the magnetic field strongest?
A. Outside the coil C. At the north pole
B. Inside the coil D. At the south pole
20. What is a typical coil voltage for a low-voltage relay circuit?
A. 2 VDC C. 12 VDC
B. 5 VDC D. 120 VDC
21. Electromagnetic stepping switches operate by
A. pulsing current to the electromagnet.
B. energizing a set and then reset coil.
C. placing 24 VDC on the coil and letting the switch cycle automatically.
D. placing a control voltage on the contacts of the switch.
22. The center of a bar magnet where no magnetic force is present is called the
A. pole. C. axis.
B. neutral line. D. keeper.
23. If you double the distance an object is away from a source of magnetism, how much loss will there be
in magnetic flux?
A. The flux will be one-half as strong.
B. The flux will be one-quarter as strong.
C. The flux will be one-fifth as strong.
D. The flux will be one-eighth as strong.
24. What is the amount of MMF generated by a 50-turn electromagnetic coil supplied by 12 VDC at a
current of one ampere?
A. 12 ampere-turns C. 50 ampere-turns
B. 38 ampere-turns D. 600 ampere-turns
25. Which of the following relative permeability values describes a vacuum?
A. 1 C. 100
B. 50 D. 1,000
10. What theory of current flow says that electric current flows from the positive side of the source,
through the load, to the negative side of the source?
A. Electron theory C. Static theory
B. Conventional theory D. Magnetic theory
11. An artificial magnet made by pressing magnetic powder together under high pressure and temperature
is called a
A. powder core magnet. C. polyform magnet.
B. rare earth magnet. D. semisteel magnet.
12. If a current of 5 amperes flows through a coil made up of 40 turns of wire, the amount of MMF generated
is
A. 8 ampere-turns. C. 45 ampere-turns.
B. 35 ampere-turns. D. 200 ampere-turns.
13. Which of the following are used to connect a DC power supply to the armature of a DC motor?
A. Field poles C. Carbon brushes
B. Armature poles D. Plungers
14. The opposition to magnetic flux as it flows through a magnetic circuit is
A. reluctance. C. permeability.
B. hysteresis. D. resistance.
15. What happens to a magnetic material when further application of MMF brings only a slight change in
magnetism in the material?
A. The material begins to heat rather than absorb more magnetism.
B. The material begins to lose its magnetic properties.
C. The material is termed saturated.
D. The material is said to have low hysteresis.
16. When using Fleming’s right-hand rule for generator action of electromagnetic induction, the forefinger
points in the direction of the
A. current flow. C. coils windings.
B. conductor motion. D. magnetic flux.
17. What part of a relay is used to support the major components of the relay?
A. Armature C. Contact spring
B. Frame D. Contact set
18. When a voltage is induced on a moving conductor in a magnetic field, current will only flow if the
conductor is
A. formed into a coil. C. part of a closed circuit.
B. moving slowly. D. large enough in diameter.
19. In a solenoid, where is the magnetic field strongest?
A. Outside the coil C. At the north pole
B. Inside the coil D. At the south pole
20. What is a typical coil voltage for a low-voltage relay circuit?
A. 2 VDC C. 12 VDC
B. 5 VDC D. 120 VDC
21. Electromagnetic stepping switches operate by
A. pulsing current to the electromagnet.
B. energizing a set and then reset coil.
C. placing 24 VDC on the coil and letting the switch cycle automatically.
D. placing a control voltage on the contacts of the switch.
22. The center of a bar magnet where no magnetic force is present is called the
A. pole. C. axis.
B. neutral line. D. keeper.
23. If you double the distance an object is away from a source of magnetism, how much loss will there be
in magnetic flux?
A. The flux will be one-half as strong.
B. The flux will be one-quarter as strong.
C. The flux will be one-fifth as strong.
D. The flux will be one-eighth as strong.
24. What is the amount of MMF generated by a 50-turn electromagnetic coil supplied by 12 VDC at a
current of one ampere?
A. 12 ampere-turns C. 50 ampere-turns
B. 38 ampere-turns D. 600 ampere-turns
25. Which of the following relative permeability values describes a vacuum?
A. 1 C. 100
B. 50 D. 1,000

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