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1.0.0
MCQ
4141. The energy band in which free electrons exist is--
first band
conduction band
second band
valence band
ব্যাখ্যা: The electrons occupying this band are called conduction electrons and the band is called the conduction band this band may be empty or partially filled. In this band, electrons move freely.
4142. The maximum efficiency of a half-wave diode rectifier is --
50%
25%
40.0%
81.2%
4143. An alternating current is converted to direct current by-
dynamo
rectifier
transformer
motor
ব্যাখ্যা: A rectifier is a device which converts ac (alternating current) to de (direct current) which flows in only one direction. This process is know as rectification.
4144. RC coupling is used for---amplification.
voltage
power
current
none
4145. Class-B power amplifier- miximum collector efficiency কত %
25
78.5
50
60
4146. What is the full name of LCD?
Light control diode .
Light crystal display.
Liquid crystal diode.
Liquid crystal display.
4147. In an LC oscillator, the frequency of oscillation is:
Proportional to LC
Proportional to square root of LC
Inversely proportional to the square root of LC
Independent of the value of LC
4148. Process of adding impurities to semiconductor is called-
mixing
refining
diffusing
doping
ব্যাখ্যা: The process of adding controlled inpurities to a semiconductor is known as "doping" The amount of impurity, or dopant, added to as intrinsic (pure) semiconductor varies its level of conductivity.
4149. At absolute zero temperanre (-273°C), an intrinsic semiconductor has-
a few free electrons.
many holes.
many free electrons.
no holes or free electrons.
ব্যাখ্যা : At absolute zero temperature (-273°C), an intrinsic semiconductor has no holes or free electrons.
4150. When there is no forbidden region between the conductance band and valence band, the substance is called:
Semiconductor.
conductor
superconductor
insulator
4151. If, line frequency is 50 Hz, then output (Hz) of a bridge rectifier is-
25
100
50
None
ব্যাখ্যা: Output frequency of bridge rectifier is twice the input frequency. Full wave bridge rectifier, 25,2x50=100H
4152. Transistor biasing represents --conditions.
ac
both ac & dc
dc
none
4153. If a power supply has no-load and full-load voltages of 30V and 25V respectively, then the percentage voltage regulation is:
10%
20%
15%
25%
4154. When transistor is used as an amplifier, it is operated in the:
Cut off region
Saturation region
Active region
Both a and b
4155. At what relgon a transistor operates --
Artlive
Saturatioit
Cut off
None
4156. Emitter follower is used for--
Impedance matching
Current gain
Voltage gain
None of the above
4157. Which one is the smallest region in a transistor?
base
collector
emitter
both (a) and (b)
ব্যাখ্যা: The base region of a BJT transistor is very thin and is lightly doped with current carries. It is the region of a transistor which has opposite polarity charge carries from the emitter and the collector regions.
4158. Half-wave rectifier- maximum efficiency--%
25
50
40.6
81.2
4159. The point of intersection of de and ac load lines is called-
saturation
operating
cut off
none of these
4160. A pn junction acts as a-
unidirectional switch.
bidirecctional switch.
controlled switch.
both unidirectional and bidirectional.
ব্যাখ্যা : The PN junction is conduct with forward bias only. It means they conduct in only one direction (Current flows from P to N). That's why PN Junction acts as unidirectional switch.