chapter 9 Flashcards
Which of the following design features must be included for a photocell to successfully work for many years?
Ability to withstand extreme temperatures
High operation cycle at rated load
Impact-resistive housing
Lightning protection
The ? conductor is the switch leg from a photoeye to a lighting contactor.
red
A common mistake in wiring a photocell is terminating the black conductor of the photoeye to the load and the red conductor of the photoeye to the source voltage.
true
A polarized reflector changes the ? of the transmitter’s polarized beam as it reflects it back to the receiver.
polarity
Without a polarized reflector being used to change the polarity of the beam on a conveyor, a shiny object might fool the receiver into thinking the beam has not been broken.
true
Which of the following is an advantage of photo-operated devices?
No contact bounce problem Incorrect
No mechanical parts to wear out Incorrect
Operate at very high speeds
Which of the following is not a category of photo-operated devices?
Photoresistive
? devices are imperative in high speed switching circuits.
Photoemissive
The resistance of a(n) ? device reduces when exposed to light.
photoconductive
The most common photoconductive device is the ? .
cad cell
What determines the amount of voltage produced by a photovoltaic cell?
The material from which it is made (0.5 V per cell for silicon)
What determines the amount of current produced by a solar cell?
The size of the surface area (larger area = more current)
? devices emit electrons when light is present.
Photoemissive
Which of the following devices emit electrons when in the presence of light?
Photodiode Incorrect
Photo SCR Incorrect
Phototransistor
