CBSE
Multiple Choice QuestionsCarbon, silicon and germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by respectively. Which one of the following relationships is true in their case?
The amplification factor of a triode valve is 15. If the grid voltage is changed by 0.3 V, the change in plate voltage in order to keep the current constant (in volt) is :
0.02
0.002
4.5
5.0
In the CB mode of a transistor, when the collector voltage is changed by 0.5 volt, the collector current changes by 0.05 mA. The output resistance will be
10 kΩ
20 kΩ
5 kΩ
2.5 kΩ
The total energy of an electron in the first excited state of hydrogen is about -3.4 eV. Its kinetic energy in this state is
-3.4 eV
-6.8 eV
6.8 eV
3.4 eV
Which logic gate is represented by the following combination of logic gates?
OR
NOR
AND
NAND
Zener diode is used for
producing oscillations in an oscillator
amplification
stabilisation
rectification
Choose the only false statement from the following
Substances with energy gap ofthe order of 10 eV are insulators
The conductivity of a semiconductor increases with increases in temperature
In conductors the valence and conduction bands may overlap
The resistivity of a semiconductor increases with increase in temperature
In junction diode, the holes are because of
Missing electrons
extra electrons
protons
neutrons
The slope of plate characteristic and mutual characteristic curves of a triode valve is 0.02 mA / V and 1 mA / V. The amplification factor of triode valve is
20
50
40
The principle of LASER action involves
amplification of particular frequency emitted by the system
population inversion
stimulated emission
All of the above
