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
Inside the coil and no way any of us is going to do all your work for you.
19. The magnetic field in a solenoid is strongest inside the coil (Option B). This occurs because a solenoid is a tightly wound coil of wire that generates a magnetic field when an electric current flows through it. Due to the close proximity of the wire turns, the magnetic field lines become concentrated and stronger inside the coil.
20. The typical coil voltage for a low-voltage relay circuit is usually 12 VDC (Option C). However, it is important to note that the specific coil voltage can vary depending on the application and the design requirements of the circuit.
21. Electromagnetic stepping switches operate by pulsing current to the electromagnet (Option A). These switches use the principle of magnetism to control the movement of the switch contacts. By applying a pulse of current to the electromagnet, the magnetic field generated causes the switch to move to the desired position.
22. The center of a bar magnet where no magnetic force is present is called the neutral line (Option B). This region is referred to as the neutral line because the magnetic field lines from each pole of the magnet cancel out each other, resulting in no net magnetic force.
23. If you double the distance an object is away from a source of magnetism, the magnetic flux will be one-quarter as strong (Option B). This relationship is based on the inverse square law, which states that the magnetic field strength decreases with the square of the distance from the source.
24. The amount of MMF (Magnetomotive Force) generated by a 50-turn electromagnetic coil supplied by 12 VDC at a current of one ampere is 600 ampere-turns (Option D). The MMF is calculated by multiplying the number of turns in the coil by the current flowing through it.
25. A vacuum has a relative permeability value of 1 (Option A). Relative permeability is a measure of how easily a material can conduct magnetic flux compared to a vacuum. Since a vacuum has no magnetic properties, its relative permeability is considered to be 1.