CBSE
Multiple Choice QuestionsRegarding a semiconductor which one of the following is wrong?
There are no free electrons at room temperature
There are no free electrons at 0K
The number of free electrons increases with the rise of temperature
The charge carriers are electrons and holes
When a p-n junction diode is connected to a battery with its p-side to positive terminal and n-side to negative terminal, the width of the depletion layer
decreases
increases
first decreases then increases
first increases then decreases
In forward and reverse biasing of a p-n junction diode, the ratio of resistances is
102 : 1
10-2 : 1
1 : 104
1 : 10-4
A n-type semiconductor is
negatively charged
positively charged
neutral
none of the above
The energy gap between the valence band and the conduction band for a material is 6 eV. The material is
an insulator
a metal
an intrinsic semiconductor
a superconductor
Which of the following statements is true for an n-type semi-conductor?
The donor level lies closely below the bottom of the conduction band
The donor level lies closely above the top of the valence band
The donor level lies at the halfway mark of the forbidden energy gap
None of the above
Avalanche breakdown in a p-n junction diode is due to
shift of fermi level
widening of forbidden gap
high impurity concentration
cummulative effect of conduction band electrons collision
To which logic gate does the truth table given below correspond?
AND
OR
NAND
XOR
An AC signal of 50 Hz frequency is input of a full wave rectifier using two diodes. The output frequency after full wave rectification is
25 Hz
50 Hz
100 Hz
200 Hz
A p-type semiconductor is formed by adding 1 indium atom in to a sample of silicon per 5x10−7 silicon atoms. If the density of atoms in the sample is 5×1028 atoms/metre3, the number of atoms accepted in per metre3 of silicon is
1.0 × 1013 atoms/cm3
2.5 × 1020 atoms/cm3
2.5 × 1025 atoms/cm3
1.0 × 1015 atoms/cm3
