Amateur Extra E6F: Optoelectronics and solar cells
These are the 11 official questions in group E6F 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.
- E6F01Question 1
What absorbs the energy from light falling on a photovoltaic cell?
- AProtons
- BPhotons
- CElectrons Correct
- DHoles
Why: Electrons absorb the energy of the light.
- E6F02Question 2
What happens to photoconductive material when light shines on it?
- AResistance decreases Correct
- BResistance increases
- CReflectivity increases
- DReflectivity decreases
Why: Light lowers the resistance of photoconductive material.
- E6F03Question 3
What is the most common configuration of an optoisolator or optocoupler?
- AA lens and a photomultiplier
- BA frequency-modulated helium-neon laser
- CAn amplitude-modulated helium-neon laser
- DAn LED and a phototransistor Correct
Why: An optoisolator is typically an LED and a phototransistor.
- E6F04Question 4
What is the photovoltaic effect?
- AThe conversion of voltage to current when exposed to light
- BThe conversion of light to electrical energy Correct
- CThe effect that causes a photodiode to emit light when a voltage is applied
- DThe effect that causes a phototransistor’s beta to decrease when exposed to light
Why: The photovoltaic effect converts light into electrical energy.
- E6F05Question 5
Which of the following describes an optical shaft encoder?
- AA device that detects rotation by interrupting a light source with a patterned wheel Correct
- BA device that measures the strength of a beam of light using analog-to-digital conversion
- CAn optical computing device in which light is coupled between devices by fiber optics
- DA device for generating RTTY signals by means of a rotating light source
Why: A shaft encoder detects rotation with a patterned wheel that interrupts light.
- E6F06Question 6
Which of these materials is most commonly used to create photoconductive devices?
- APolyphenol acetate
- BArgon
- CCrystalline semiconductor Correct
- DAll these choices are correct
Why: Photoconductive devices are usually made from crystalline semiconductors.
- E6F07Question 7
What is a solid-state relay?
- AA relay that uses transistors to drive the relay coil
- BA device that uses semiconductors to implement the functions of an electromechanical relay Correct
- CA mechanical relay that latches in the on or off state each time it is pulsed
- DA semiconductor switch that uses a monostable multivibrator circuit
Why: A solid-state relay does a mechanical relay's job using semiconductors.
- E6F08Question 8
Why are optoisolators often used in conjunction with solid-state circuits that control 120 VAC circuits?
- AOptoisolators provide a low-impedance link between a control circuit and a power circuit
- BOptoisolators provide impedance matching between the control circuit and power circuit
- COptoisolators provide an electrical isolation between a control circuit and the circuit being switched Correct
- DOptoisolators eliminate the effects of reflected light in the control circuit
Why: Optoisolators electrically isolate the control circuit from the switched circuit.
- E6F09Question 9
What is the efficiency of a photovoltaic cell?
- AThe output RF power divided by the input DC power
- BThe output in lumens divided by the input power in watts
- CThe open-circuit voltage divided by the short-circuit current under full illumination
- DThe relative fraction of light that is converted to current Correct
Why: Efficiency is the fraction of light converted to current.
- E6F10Question 10
What is the most common material used in power-generating photovoltaic cells?
- ASelenium
- BSilicon Correct
- CCadmium sulfide
- DIndium arsenide
Why: Most power-generating solar cells are silicon.
- E6F11Question 11
What is the approximate open-circuit voltage produced by a fully illuminated silicon photovoltaic cell?
- A0.5 volts Correct
- B0.7 volts
- C1.1 volts
- D1.5 volts
Why: A silicon cell produces about 0.5 V open-circuit in full sun.