magnetic and nonmagnetic materials

magnetic and nonmagnetic materials

The path around a magnet in which the lines of force move is called a magnetic A. zone. B. force. C. circuit. D. sphere.

2. How many ampere-turns of MMF is produced if a current of 6 A is applied through a winding of 100 turns of wire? A. 600 ampere-turns B. 106 ampere-turns C. 160 ampere-turns D. 16.67 ampere-turns

3. What is the amount of MMF generated by a 50-turn electromagnetic coil supplied by 12?VDC at a current of one ampere? A. 38 ampere-turns B. 600 ampere-turns C. 12 ampere-turns D. 50 ampere-turns

4. The center of a bar magnet where no magnetic force is present is called the A. pole. B. neutral line. C. keeper. D. axis.

5. When using Fleming’s left-hand rule or motor rule, the thumb points in the direction of A. the magnetic lines of force. B. coil windings. C. current flow. D. conductor motion.

6. How many ampere-turns of MMF is produced if a current of 2.2 A is applied through a winding of 200 turns of wire? A. 90.90 ampere-turns B. 440 ampere-turns C. 197.8 ampere-turns D. 220 ampere-turns

7. A magnetic circuit in which the lines of force pass through both magnetic and nonmagnetic materials is called a A. full magnetic circuit. B. complete magnetic circuit. C. closed magnetic circuit. D. compound magnetic circuit.

8. The value 100,000,000 Maxwells is equal to A. 1 Weber. B. 4 Webers. C. 100 Webers. D. 10 Webers.

9. If you dip a bar magnet into iron filings, the filings will stick to A. both poles of the magnet. B. only the north pole of the magnet. C. the whole magnet. D. only the south pole of the magnet.

10. In a solenoid, where is the magnetic field strongest? A. Outside the coil B. Inside the coil C. At the south pole D. At the north pole

11. 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 B. Static theory C. Conventional theory D. Magnetic theory

12. Which of the following illustrations shows a closed magnetic circuit? A. B. C. D.

13. As compared to iron, how much more resistance does a nonmagnetic material produce against magnetic lines of force? A. 20,000 times as much resistance B. 200 times as much resistance C. 20 times as much resistance D. 2,000 times as much resistance

14. How do lines of magnetic force travel? A. From the magnet’s south pole to its north pole B. From the magnet’s poles to its neutral line C. From the magnet’s north pole to its south pole D. From the magnet’s neutral line to its poles

15. A device that helps a horseshoe magnet retain its magnetism is called A. keeper. B. block. C. shunt. D. shorting bar.

16. Which of the following is a magnetic material? A. Glass B. Wood C. Paper D. Iron

17. Magnetic flux is pushed through a magnetic path by A. magnetomotive force. B. hysteresis. C. reluctance. D. electromotive force.

18. 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-eighth as strong. C. The flux will be one-quarter as strong. D. The flux will be one-fifth as strong.

19. How can you easily locate the north pole of an unmarked bar magnet? A. Sprinkle iron filings on the bar magnet. More filings will be attracted to the north pole. B. Place a compass near one end of the magnet. The north pole of the compass will be attracted to the north pole of the magnet. C. Place a compass near one end of the magnet. The south pole of the compass will be attracted to the north pole of the bar magnet. D. Cover the bar magnet with filings and lightly thump the magnet against a table. The south pole will retain more of the filings.

20. An artificial magnet made by pressing magnetic powder together under high pressure and temperature is called a A. semisteel magnet. B. powder core magnet. C. polyform magnet. D. rare earth magnet.

21. The opposition to magnetic flux as it flows through a magnetic circuit is A. permeability. B. hysteresis. C. resistance. D. reluctance.

22. What is a typical coil voltage for a low-voltage relay circuit? A. 2 VDC B. 5 VDC C. 120 VDC D. 12 VDC

23. The area of space around a magnet in which the lines of force flow is called the A. magnetic zone B. magnetic field C. magnetic flux D. magnetic sphere

24. 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 lose its magnetic properties. B. The material is said to have low hysteresis. C. The material begins to heat rather than absorb more magnetism. D. The material is termed saturated.

25. Which of the following relative permeability values describes a vacuum? A. 1 B. 1,000 C. 50 D. 100

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