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Extra Class Exam Question Pool

effective 7/01/2016 thru 6/29/2020

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2016-E6D: Toroidal and Solenoidal Inductors: permeability, core material, selecting, winding; transformers; Piezoelectric devices

2016-E6D01: How many turns will be required to produce a 5-microhenry inductor using a powdered-iron toroidal core that has an inductance index (A L) value of 40 microhenrys/100 turns?

35 turns

13 turns

79 turns

141 turns



2016-E6D02: What is the equivalent circuit of a quartz crystal?

Motional capacitance, motional inductance, and loss resistance in series, all in parallel with a shunt capacitor representing electrode and stray capacitance

Motional capacitance, motional inductance, loss resistance, and a capacitor representing electrode and stray capacitance all in parallel

Motional capacitance, motional inductance, loss resistance, and a capacitor representing electrode and stray capacitance all in series

Motional inductance and loss resistance in series, paralleled with motional capacitance and a capacitor representing electrode and stray capacitance



2016-E6D03: Which of the following is an aspect of the piezoelectric effect?

Mechanical deformation of material by the application of a voltage

Mechanical deformation of material by the application of a magnetic field

Generation of electrical energy in the presence of light

Increased conductivity in the presence of light



2016-E6D04: Which materials are commonly used as a slug core in a variable inductor?

Ferrite and brass

Polystyrene and polyethylene

Teflon and Delrin

Cobalt and aluminum



2016-E6D05: What is one reason for using ferrite cores rather than powdered-iron in an inductor?

Ferrite toroids generally require fewer turns to produce a given inductance value

Ferrite toroids generally have lower initial permeability

Ferrite toroids generally have better temperature stability

Ferrite toroids are easier to use with surface mount technology



2016-E6D06: What core material property determines the inductance of a toroidal inductor?

Permeability

Thermal impedance

Resistance

Reactivity



2016-E6D07: What is the usable frequency range of inductors that use toroidal cores, assuming a correct selection of core material for the frequency being used?

From less than 20 Hz to approximately 300 MHz

From a few kHz to no more than 30 MHz

From approximately 10 Hz to no more than 3000 kHz

From about 100 kHz to at least 1000 GHz



2016-E6D08: What is one reason for using powdered-iron cores rather than ferrite cores in an inductor?

Powdered-iron cores generally maintain their characteristics at higher currents

Powdered-iron cores generally have greater initial permeability

Powdered-iron cores generally require fewer turns to produce a given inductance

Powdered-iron cores use smaller diameter wire for the same inductance



2016-E6D09: What devices are commonly used as VHF and UHF parasitic suppressors at the input and output terminals of a transistor HF amplifier?

Ferrite beads

Electrolytic capacitors

Butterworth filters

Steel-core toroids



2016-E6D10: What is a primary advantage of using a toroidal core instead of a solenoidal core in an inductor?

Toroidal cores confine most of the magnetic field within the core material

Toroidal cores make it easier to couple the magnetic energy into other components

Toroidal cores exhibit greater hysteresis

Toroidal cores have lower Q characteristics



2016-E6D11: How many turns will be required to produce a 1-mH inductor using a core that has an inductance index (A L) value of 523 millihenrys/1000 turns?

43 turns

2 turns

4 turns

229 turns



2016-E6D12: What is the definition of saturation in a ferrite core inductor?

The ability of the inductor's core to store magnetic energy has been exceeded

The inductor windings are over coupled

The inductor's voltage rating is exceeded causing a flashover

Adjacent inductors become over-coupled



2016-E6D13: What is the primary cause of inductor self-resonance?

Inter-turn capacitance

The skin effect

Inductive kickback

Non-linear core hysteresis



2016-E6D14: Which type of slug material decreases inductance when inserted into a coil?

Brass

Ceramic

Ferrite

Powdered-iron



2016-E6D15: What is current in the primary winding of a transformer called if no load is attached to the secondary?

Magnetizing current

Direct current

Excitation current

Stabilizing current



2016-E6D16: What is the common name for a capacitor connected across a transformer secondary that is used to absorb transient voltage spikes?

Snubber capacitor

Clipper capacitor

Trimmer capacitor

Feedback capacitor



2016-E6D17: Why should core saturation of a conventional impedance matching transformer be avoided?

Harmonics and distortion could result

Magnetic flux would increase with frequency

RF susceptance would increase

Temporary changes of the core permeability could result





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