Amateur Extra E6D: Crystals and magnetic cores
These are the 11 official questions in group E6D of the 2024–2028 Amateur Extra question pool, with the correct answer marked and a plain-English explanation of why it's right. The real exam asks one question from this group.
Learn E6D step by stepThe Amateur Extra course teaches this group in a short guided lesson, then drills you on the questions you miss. Start with the free lessons to see how it works.
- E6D01Question 1
What is piezoelectricity?
- AThe ability of materials to generate electromagnetic waves of a certain frequency when voltage is applied
- BA characteristic of materials that have an index of refraction which depends on the polarization of the electromagnetic wave passing through it
- CA characteristic of materials that generate a voltage when stressed and that flex when a voltage is applied Correct
- DThe ability of materials to generate voltage when an electromagnetic wave of a certain frequency is applied
Why: Piezoelectric materials make a voltage when stressed and flex when a voltage is applied.
- E6D02Question 2
What is the equivalent circuit of a quartz crystal?
- ASeries RLC in parallel with a shunt C representing electrode and stray capacitance Correct
- BParallel RLC, where C is the parallel combination of resonance capacitance of the crystal and electrode and stray capacitance
- CSeries RLC, where C is the parallel combination of resonance capacitance of the crystal and electrode and stray capacitance
- DParallel RLC, where C is the series combination of resonance capacitance of the crystal and electrode and stray capacitance
Why: A crystal acts like a series RLC in parallel with a shunt capacitance.
- E6D03Question 3
Which of the following is an aspect of the piezoelectric effect?
- AMechanical deformation of material due to the application of a voltage Correct
- BMechanical deformation of material due to the application of a magnetic field
- CGeneration of electrical energy in the presence of light
- DIncreased conductivity in the presence of light
Why: Applying a voltage mechanically deforms a piezoelectric material.
- E6D04Question 4
Why are cores of inductors and transformers sometimes constructed of thin layers?
- ATo simplify assembly during manufacturing
- BTo reduce power loss from eddy currents in the core Correct
- CTo increase the cutoff frequency by reducing capacitance
- DTo save cost by reducing the amount of magnetic material
Why: Thin layers reduce eddy-current losses in the core.
- E6D05Question 5
How do ferrite and powdered iron compare for use in an inductor core?
- AFerrite cores generally have lower initial permeability
- BFerrite cores generally have better temperature stability
- CFerrite cores generally require fewer turns to produce a given inductance value Correct
- DFerrite cores are easier to use with surface-mount technology
Why: Ferrite cores usually need fewer turns for the same inductance.
- E6D06Question 6
What core material property determines the inductance of an inductor?
- APermittivity
- BResistance
- CReactivity
- DPermeability Correct
Why: Core permeability determines inductance.
- E6D08Question 7
Which of the following materials has the highest temperature stability of its magnetic characteristics?
- ABrass
- BPowdered iron Correct
- CFerrite
- DAluminum
Why: Powdered iron has the most temperature-stable magnetic properties.
- E6D09Question 8
What devices are commonly used as VHF and UHF parasitic suppressors at the input and output terminals of a transistor HF amplifier?
- AElectrolytic capacitors
- BButterworth filters
- CFerrite beads Correct
- DSteel-core toroids
Why: Ferrite beads suppress VHF/UHF parasitics on amplifier leads.
- E6D10Question 9
What is a primary advantage of using a toroidal core instead of a solenoidal core in an inductor?
- AToroidal cores confine most of the magnetic field within the core material Correct
- BToroidal cores make it easier to couple the magnetic energy into other components
- CToroidal cores exhibit greater hysteresis
- DToroidal cores have lower Q characteristics
Why: A toroid keeps most of the magnetic field inside the core.
- E6D11Question 10
Which type of core material decreases inductance when inserted into a coil?
- ACeramic
- BBrass Correct
- CFerrite
- DAluminum
Why: A brass core decreases inductance.
- E6D12Question 11
What causes inductor saturation?
- AOperation at too high a frequency
- BSelecting a core with low permeability
- COperation at excessive magnetic flux Correct
- DSelecting a core with excessive permittivity
Why: Too much magnetic flux saturates an inductor.
Learn E6D step by stepThe Amateur Extra course teaches this group in a short guided lesson, then drills you on the questions you miss. Start with the free lessons to see how it works.