NAVEDTRA 14174A, NEETS Mod. 2, Ch.1 Flashcards
Which type of current regularly changes direction?
Alternating
What is the amplitude of direct current in a wire when a coulomb of electrons moves past a point in a wire in one second and all of the electrons are moving in the same direction?
One ampere
Which type of current is practically used by all modern commercial electric power companies?
Alternating
Which type of device can step up or down alternating voltages amplitudes?
Transformer
Which type of patterns are plotted on graph paper that result from changes in amplitude with respect to time?
Waveform
What is the most commonly used means for producing or using electricity?
Magnetism
What year did Hans Christian Oersted discover a definite relationship between magnetism and electricity?
1819
Which conductor rule can the relation between the direction of the magnetic lines of force around a conductor and the direction of electron current flow in the conductor be determined?
Left-Hand rule
Which unit indicates one cycle per second?
Hertz (Hz)
What is the number of complete cycles of alternating current or voltage completed each second referred to as?
Frequency
What is frequency always measured and expressed in?
Hertz
What is the time required to complete one cycle of a waveform called?
Period
What is the distance from zero to the maximum value of each alternation called?
Amplitude
What is the distance along the waveform from one point to the same point on the next cycle called?
Wavelength
How many maximum or AC peak values during each complete cycle of AC are there?
Two
What are alternating voltage and current usually expressed in?
Effective values
Which alternating voltage or current value is the value of voltage or current at one particular instant?
Instantaneous
What is the value of alternating voltage or current that will have the same effect on a resistance as a comparable value of direct voltage or current will have on the same resistance?
Effective
Which method is the rate at which heat is produced in a resistance form a convenient basis for establishing an effective value of alternating current known as?
Heating effect
Which law states that current is directly proportional to the applied voltage?
Ohms law
What are two sine waves that are precisely in step with one another said to be?
In phase
What is the amount by which one sine wave leads or lags another sine wave measured in?
Degrees
Which type of elements are resistors, lamps, and heating elements examples of?
Resistive
What is formed by wire wound around a core?
Coil
What is the effect called when a conductor is in a magnetic field and either the field or the conductor moves, an emf (voltage) is induced in the conductor?
Magnetic induction
What is the maximum value reached during one alternation of a sine wave called?
Peak Value
The average value of a sine wave of voltage or current is the average of all the instantaneous values during one alternation. The average value is equal to what amount of the peak value?
0.636
How many times the peak value is the effective value of a sine wave?
0.707
