This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Photoelectric Transducers”.
1. Optical radiations involve _________
a) optoelectric devices
b) biological devices
c) mechanical devices
d) chemical devices
View Answer
Explanation: Emission and absorption of optical radiations are carried out by making use of optoelectric devices.
2. Photoelectric transducers consist of _______
a) 1 transducer
b) 3 transducers
c) 5 transducers
d) 10 transducers
View Answer
Explanation: A photoelectric transducer consists of 3 transducers. They are as follows:
Photo-emissive
Photo-conductive
Photo-voltaic.
3. Photoconductive transducers produce output ________
a) due to change in inductance
b) due to change in light
c) due to change in resistance
d) due to change in temperature
View Answer
Explanation: A photoconductive transducer produces an output due to a change in the resistance. Electrical output is produced due to a variation in the temperature.
4. Commonly used photoemissive material is _______
a) gold
b) opium
c) tellurium
d) cesium-antimony
View Answer
Explanation: Cesium-antimony is the most commonly used photoemissive material. The photoemissive material is housed in a glass tube. Photoemissive devices are also called as phototubes.
5. Phototubes are very quick in response to light.
a) True
b) False
View Answer
Explanation: Phototubes are quick in response to light. Phototubes are used in applications which require light pulses of very short durations to be observed.
6. Photoconductors are made of _______
a) thick layer of semiconductor
b) thin layer of semiconductor
c) capacitive substrate
d) inductive substrate
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Explanation: Photoconductors comprise of a thin layer of semiconductor. Photoconductors not consisting of a junction are known as junction less detectors.
7. When an open circuited pn junction is illuminated then _________________
a) resistance increases
b) there is no effect
c) electron hole pairs are formed
d) capacitance increases
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Explanation: Upon illumination of an open circuited pn junction, electron hole pairs are generated. A small voltage appears across the junction and as a result it acts as a voltae source.
8. Optocoupler consists of a phototransistor and a led.
a) True
b) False
View Answer
Explanation: The optocoupler consists of a phototransistor and an infrared emitting diode. Wavelength of the emitting and receiving diodes must be matched in order to get a proper output.
9. Response time for gas-filled phototubes is _______
a) zero
b) intermediate
c) fast
d) slow
View Answer
Explanation: Gas filled phototubes are generally very slow in response as compared to vacuum phototubes. This is due to the slow movement of ions towards the photocathode.
10. Reverse leakage current in a transistor _______
a) is affected by light
b) is not affected by light
c) increases with a decrease in pressure
d) decreases with increase in temperature
View Answer
Explanation: The reverse leakage current in a transistor is directly proportional to the intensity of light. It increases with the increase in light intensity.
Sanfoundry Global Education & Learning Series – Electrical Measurements.
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