AFI 178.doc

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1.   Which of the following metals is ferrous?

A. Brass
B. Aluminum
C. Copper
D. Cast iron

2.   In a solenoid, where is the magnetic field strongest?

A. Inside the coil
B. Outside the coil
C. At the north pole
D. At the south pole

3.   The area of space around a magnet in which the lines of force flow is called the

A. magnetic sphere
B. magnetic zone
C. magnetic flux
D. magnetic field

4.   The area inside the hysteresis loop represents

A. residual magnetism.
B. magnetic saturation.
C. energy.
D. permeability.

5.   Which of the following are used to connect a DC power supply to the armature of a DC motor?

A. Plungers
B. Armature poles
C. Carbon brushes
D. Field poles

6.   The moveable metal object located inside a solenoid is called

A. an armature.
B. a slider.
C. a plunger.
D. a frame.

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

8.   If the force of a magnet produces one weber per square meter, the flux density is equal to one

A. gauss.
B. henery.
C. Telsa.
D. maxwell.

9.   The ratio of the permeability of a material to the permeability of a vacuum is called

A. coercive permeability.
B. relative permeability.
C. residual permeability.
D. saturation permeability.

10.   Which of the following is a magnetic material?
A. Paper
B. Glass
C. Iron
D. Wood
11.   Which of the following relative permeability values describes a vacuum?

A. 1
B. 50
C. 100
D. 1,000

12.   If a piece of iron is placed near a magnet, the iron will behave like a magnet due to magnetic

A. induction.
B. interference.
C. coupling.
D. reversal.

13.   The value 100,000,000 Maxwells is equal to

A. 10 Webers.
B. 1 Weber.
C. 100 Webers.
D. 4 Webers.

14.   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
B. 50 ampere-turns
C. 38 ampere-turns
D. 600 ampere-turns

15.   If a current of 5 amperes flows through a coil made up of 40 turns of wire, the amount of MMF generated is

A. 200 ampere-turns.
B. 45 ampere-turns.
C. 8 ampere-turns.
D. 35 ampere-turns.

16.   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 termed saturated.
C. The material is said to have low hysteresis.
D. The material begins to heat rather than absorb more magnetism.

17.   When using Fleming’s left-hand rule or motor rule, the thumb points in the direction of

A. current flow.
B. conductor motion.
C. coil windings.
D. the magnetic lines of force.

18.   How can you easily locate the north pole of an unmarked bar magnet?

A. 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.
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. Cover the bar magnet with filings and lightly thump the magnet against a table. The south pole will retain more of the filings.
D. Sprinkle iron filings on the bar magnet. More filings will be attracted to the north pole.

19.   When a voltage is induced on a moving conductor in a magnetic field, current will only flow if the conductor is
A. large enough in diameter.
B. part of a closed circuit.
C. moving slowly.
D. formed into a coil.

20.   Which theory of current flow states that electric current flows from the negative side of the source, through the load, and back to the positive side of the source?
A. Magnetic Theory
B. Electron Theory
C. Static Theory
D. Conventional Theory

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

22.   What part of a relay is used to support the major components of the relay?
A. Armature
B. Frame
C. Contact set
D. Contact spring

23.   As compared to iron, how much more resistance does a nonmagnetic material produce against magnetic lines of force?

A. 2,000 times as much resistance
B. 20 times as much resistance
C. 20,000 times as much resistance
D. 200 times as much resistance

24.   In the following figure, a conductor is connected to a battery and placed between two compasses. An electric current is then passed through the conductor. In what direction do the north poles of the compasses point?

A. In the same direction as the flow of current through the conductor
B. In the same direction as the magnetic lines of force
C. In the opposite direction from the magnetic lines of force
D. In the opposite direction from the flow of current through the conductor

25.   The path around a magnet in which the lines of force move is called a magnetic

A. zone.
B. sphere.
C. force.
D. circuit.