Key Topic 19: Photoconductive Devices

Question 1

3-19C1: What happens to the conductivity of photoconductive material when light shines on it?

A. It increases.
B. It decreases.
C. It stays the same.
D. It becomes temperature dependent.

Answer 1

A. It increases.

Question 2

3-19C2: What is the photoconductive effect?

A. The conversion of photon energy to electromotive energy.
B. The increased conductivity of an illuminated semiconductor junction.
C. The conversion of electromotive energy to photon energy.
D. The decreased conductivity of an illuminated semiconductor junction.

Answer 2

B. The increased conductivity of an illuminated semiconductor junction.

Question 3

3-19C3: What does the photoconductive effect in crystalline solids produce a noticeable change in?

A. The capacitance of the solid.
B. The inductance of the solid.
C. The specific gravity of the solid.
D. The resistance of the solid.

Answer 3

D. The resistance of the solid.

Question 4

3-19C4: What is the description of an optoisolator?

A. An LED and a photosensitive device.
B. a P-N junction that develop an excess positive charge when exposed to light.
C. An LED and a capacitor.
D. An LED and a lithium battery cell.

Answer 4

A. An LED and a photosensitive device.

Question 5

3-19C5: What happens to the conductivity of a photosensitive semiconductor junction when it is illuminated?

A. The junction resistance is unchanged.
B. The junction resistance decreases.
C. The junction resistance becomes temperature dependent.
D. The junction resistance increases.

Answer 5

B. The junction resistance decreases.

Question 6

3-19C6: What is the description of an optocoupler?

A. A resistor and a capacitor.
B. Two light sources modulated onto a mirrored surface.
C. An LED and a photosensitive device.
D. An amplitude modulated beam encoder.

Answer 6

C. An LED and a photosensitive device.