81. In a semi conductor avalanche breakdown occurs when
a. Reverse bias exceeds the limiting value
b. Forward bias exceeds the limiting value
c. Forward current exceeds the limiting value
d. Potential barrier is reduced to zero
82. In a half wave rectifier , the load current flows
a. Only for the positive half cycle of the input signal
b. Only for the negative half cycle of the input signal
c. For full cycle
d. For less than fourth cycle
83. If 10 V is the peak voltage across the secondary of the transformer in a half wave rectifier (without any filter circuit ) then the maximum voltage on the reverse biased diode will be
a. 20 V
b. 14.14 V
c. 10 V
d. 7.8 V
84. In a centre tap full wave rectifier, 50 V is the pack voltage between the centre tap and one of the ends of the seecondary the maximum voltage across the reverse biased diode will be
a. 100 V
b. 72 V
c. 50 V
d. 38 V
85. In a zener diode
a. Forward voltage rating is high
b. Negative resistance characteristics exists
c. Sharp breakdown occurs at low reverse voltage
d. None of the above
86. Any semi-conductor material has a valence of electrons
a. 4
b. 6
c. 8
d. 3 or 5
87. A semi-conductor that is electrically neutral
a. has no majority carriers
b. has no minority carriers
c. has no free charge carriers
d. has equal amounts of positive and negative charges
88. Resistivity of a semi-conductor depends on
a. Shape of the semi-conductor
b. atomic nature semi-conductor
c. width of semi-conductor
d. length of semi-conductor
89. When holes leave the p material to fill electron in the n-material the process is called
a. mixing
b. depletion
c. diffusion
d. depletion
90. In case of selenium under the influence of varying light intensity
a. emf is generated due to chemical reaction
b. emf is generated due to physical reaction
c. electrical conductivity changes
d. the number of electrons liberated variers
