CBSE
Multiple Choice QuestionsWhich logic gate is represented by the following combination of logic gates?
OR
NAND
AND
NOR
A Ge specimen is doped with Al. The concentration of acceptor atoms is ∼ 1021 atoms/m3. Given that the intrinsic concentration of electron-hole pairs is ∼ 1019/m3, the concentration of electrons in the speimen is
1017/m3
1015/m3
104/m3
102/m3
Assertion: In a transistor the base is made thin.
Reason: A thin base makes the transistor stable.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
Assertion: In He-Ne laser, population inversion takes place between energy levels of neon atoms.
Reason: Helium atoms have a meta-stable energy level.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
Assertion: A transistor amplifier in common emitter configuration has a low input impedence.
Reason: The base to emitter region is forward biased.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
A laser beam is used for carrying out surgery because it
is highly monochromatic
is highly coherent
is highly directional
can be sharply focused
To a germanium sample, traces of gallium are added as an impurity. The resultant sample would behave like
a conductor
a p-type semiconductor
an n-type semiconductor
an insulator
In the following common emitter configuration an npn transistor with current gain β = 100 is used. The output voltage of the amplifier will be
10 mV
0.1 mV
1.0 mV
10 V
Assertion: The resistivity of a semiconductor increases with temperature.
Reason: The atoms of a semiconductor vibrate with larger amplitude at higher temperatures thereby increasing its resistivity.
if both assertion and reason are true and the reason is the correct explanation of the assertion
if both assertion and reason are true and the reason is not the correct explanation of the assertion
if assertion is true but reason is false
if both assertion and reason are false statements
Assertion: The possibility of an electric bulb fusing is higher at the time of switching on and off.
Reason: Inductive effects produce a surge at the time of switch-off and switch-on.
if both assertion and reason are true and the reason is the correct explanation of the assertion
if both assertion and reason are true and the reason is not the correct explanation of the assertion
if assertion is true but reason is false
if both assertion and reason are false statements
