Principles Flashcards
What will produce a magnetic field?
A current flowing through a conductor.
When induced currents produce expanding magnetic fields around conductors in a direction that opposes the original magnetic field, this is known as?
Lenz’s law.
What determines the field strength of the magnetic field around a conductor?
The amount of current.
They opposition to the creation of magnetic lines of force in a magnetic circuit is know as?
Reluctance
Permeability is defined as?
The ratio of magnetic flux density in a substance to the magnetizing force that produces it.
What is meant by the term “back EMF”?
A voltage that opposes the applied EMF.
What group of metals are the best low-resistance conductors?
Gold, silver, and copper
Good conductors with minimum resistance have what type of electrons?
Many free electrons.
What formula would calculate the total inductance of inductors in series?
LT = L1 + L2
How many degrees are there in one complete sine wave cycle?
360 degrees
What type of wave is characterized by a rise time significantly faster than the fall time?
Sawtooth wave
What type of wave is made up of sine waves of the fundamental frequency and all the odd harmonics?
Square
What type of wave is made up of sine waves at the fundamental frequency and all the harmonics?
Sawtooth wave
What is the basic unit of electrical power?
Watt
What formula would determine the inductive reactance of a coil if frequency and coil inductance are known?
XL = 2πfL
What is the term used to express the amount of electrical energy stored in an electrostatic field?
Joules
The product of readings of an AC voltmeter and AC ammeter is called:
Apparent power
What is the term for the out-of-phase power associated with inductors and capacitors?
Reactive power
Which metal object may be least affected by galvanic corrosion when submerged in seawater?
Stainless steel propeller shaft
What metal is usually employed as a sacrificial anode for corrosion control purposes?
Zinc bar
What is the relative dielectric constant for air?
1
Corrosion resulting from electric current flow between dissimilar metals is called?
Galvanic corrosion
Which of these will be most useful for insulation at UHF frequencies?
Mica
Skin effect is the phenomenon where?
RF current flows in a thin layer of the conductors, closer to the surface, as frequency increases.
How might you reduce the inductance of an antenna coil?
Reduce the number of turns.
What is the purpose of a bypass capacitor?
It removes alternating current by providing a low impedance path to ground.
What is the easiest voltage amplitude to measure by viewing a pure sine wave signal on an oscilloscope?
Peak-to-peak
What is the RMS voltage at a common household electrical power outlet?
117-V AC
An AC ammeter indicates?
Effective (RMS) values of current
What is the peak voltage at a common household electrical outlet?
165.5 volts
By what factor must the voltage of an AC circuit, as indicated on the scale of an AC voltmeter, by multiplied to obtain the peak voltage value?
1.414
By what factor must the voltage measured in an AC circuit, as indicated on the scale of an AC voltmeter, be multiplied to obtain the average voltage value?
0.9
What are the 5 common materials of descending conductivity?
Silver, copper, aluminum, iron, and lead
Halving the cross-sectional area of A conductor will?
Double the resistance.
What is the term used to identify an AC voltage would cause the same heating in a resistor as a corresponding value of DC voltage?
Root mean square (RMS)
What happens to receive power in a circuit that has both inductors and capacitors?
It alternates between magnetic and electric fields and is not dissipated.
Assuming a power source to have a fixed value of internal resistance, maximum power will be transferred to the load when?
The load impedance equals the internal impedance of the source.
How do you compute true power (power dissipated in the circuit) in a circuit where AC voltage and current are out of phase?
Multiply apparent power times the power factor.
What is the peak voltage at a common household electrical outlet?
165.5 volts
What will produce a magnetic field?
A current flowing through a conductor.
What are the 2 basic types of junction field-effect transistors?
N-channel and P-channel
MOSFETs are manufactured with THIS protective device from static charges and excessive voltages
Zener diode
What are the 2 most commonly-used specifications for a junction diode?
Maximum forward current and PIV (peak inverse voltage)
A common emitter amplifier has?
More voltage gain than a common collector
How does the input impedance of a field-effect transistor compare with that of a bipolar transistor?
A FET has high input impedance; a bipolar transistor has low input impedance.
What limits the maximum forward current in a junction diode?
The junction temperature
How would you calculate the total capacitance of 3 capacitors in parallel?
CT=C1+C2+C3
The opposition to the creation of magnetic lines of force in a magnetic circuit is known as?
Reluctance
What is the description of a square wave?
A wave that abruptly changes back and forth between 2 voltages levels for equal amounts of time.
What is a sine wave?
A wave whose amplitude at any given instant can be represented by the projection of a point on a wheel rotating at a uniform speed.
What device is used to store electrical energy in an electrostatic field?
Capacitor.
Which metal object may be least affected by galvanic corrosion when submerged in seawater?
Stainless steel propeller shaft.
