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MCAT Physics Mcq Questions Electronics
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MCAT Physics Mcq Questions Electronics
1
A metal rod of 25 cm length is moving at a speed of 0.5/sec in direction perpendicular to 0.25T magnetic field. Emf produced in the rod is
A
0 volt
B
3.125 volt
C
31.25 volt
D
0.03125 volt
2
The emf induced in a coil by a changing magnetic flux may have unit as
A
ms-1A
B
ms-2A-1
C
kgms2A-1
D
kgm2s-1A-1
3
A coil of wire is arranged with its plan perpendicular to a uniform magnetic field o flux density B. when the radius of the coil increases from r1 to r2 in time ?t then what is the emf induced in the coil?
A
?B/r22-r12/?t
B
?B(r2-r1)2/?t
C
?B(r22-r12)/?t
D
?B(r22+r12)/?t
4
The emf induced in a conductor of unit length moving with unit velocity at right angles to a magnetic field is equal to
A
Magnetic flux density
B
Torque
C
Mutual induction
D
Motional emf
5
The self-inductance of a solenoid is increased when a soft iron core is inserted into it. This is because the soft iron core
A
Decreases the resistance of the solenoid
B
Reduces the effect of eddy current
C
Improves the flux linkage between the turns of the coil
D
Increases the mutual inductance between the solenoid and the core
6
A small coil lies inside a large coil. The two coils are horizontal concentric and carry currents in opposite directions. The large coil will experience
A
A torque about horizontal axis
B
A torque about vertical axis
C
An upward force along the axis
D
No resultant force
7
An aeroplane of wingspan 10m flies from the equator towards the North Pole. The wings are perpendicular to the vertical component of the earths magnetic field (B = 4x10-5T). At maximum speed an emf of 96mV is induced across the wing tips. The maximum speed of the aeroplane is
A
150msec-1
B
384msec-1
C
38.4msec-1
D
200msec-1
8
A.C can not be used for
A
producing heat
B
producing light
C
Magnetizing iron
D
Producing magnetic field
9
Non inductive resistances are used in decreasing
A
Mutual inductance
B
Self inductance
C
Magnetic fields
D
Heating effect
10
Magnetic compass needle will be deflecting if it is kept near
A
Static charge
B
Soft iron
C
Semi-conductor
D
Accelerating charge
11
The alternating current has frequency of 106 Hz in such a way that time period for completion of cycle is
A
1?s
B
1.5?s
C
106sec
D
1sec
12
Long distance transmission is easy for
A
D.C voltage
B
A.C voltage
C
Half A.C voltage
D
Half D.C voltage
13
Which one of the following devices does not function like an electric motor?
A
Galvanometer
B
Ammeter
C
Voltmeter
D
Transformer
14
The out put voltage of a transformer is 3 times the input voltage then turns ratio will be
A
03-Jan
B
3
C
1
D
6
15
For long distance transmission the transformer used is
A
Step down
B
Input voltage and output voltage remain same
C
Step up
D
Amplifier is used
16
Self inductance of a long solenoid is
A
??n2?A
B
??n2A/?
C
??N2?A
D
BA
17
An electric current induced within the body of a conductor when that conductor either moves through a non uniform magnetic field or in a region where there is a change in magnetic flux is called
A
Induced current
B
Eddy current
C
Back emf
D
None of the above
18
Lagging of changes in the magnetization of a substance behind changes in the magnetic field as the magnetic field is varied is known as magnetic
A
Retaintivity
B
Permeability
C
Flux
D
Hysteresis
19
Transformer works on the principle of
A
Lenzs law
B
Faradays law
C
Mutual induction
D
Law of conservation of power
20
When the motor is at its maximum speed then back emf will be
A
Maximum
B
Zero
C
Intermediate values
D
No back emf
21
Electrons present in p-type material due to thermal pair generation are
A
majority carriers
B
minority carriers
C
dual carriers
D
blockers
22
Semi-conductors with donor atoms and free electrons belong to the type
A
n
B
p
C
mix
D
any of above
23
Semi-conductor germanium and silicon are
A
pentavalent
B
trivalent
C
divalent
D
tetravalent
24
Acceptor and donor impurities donate
A
n-carriers only
B
p-carriers only
C
p-carriers and n-carriers respectively
D
n-carriers and p-carriers respectively
25
p-n junction when reversed biased acts as a
A
capacitor
B
inductor
C
on switch
D
off switch
26
In p-n-p transistor the collector current is
A
equal to emitter current
B
slightly less than emitter current
C
greater than emitter current
D
any of above
27
In n-p-n transistor, p works as
A
collector
B
emitter
C
base
D
any of above
28
The simplest type of rectification known as half wave rectification is obtained by
A
using a transistor
B
suppressing the harmonics in A.C voltage
C
suppressing half wave of A.C supply by using diode
D
using a Coolidge tube
29
Identify the correct statement about minority carriers
A
holes in n-type and free electrons in p-type
B
holes in n-type and p-type
C
free electrons in n-type and holes in p-type
D
free electrons in n-type and p-type
30
Depletion region of a junction is formed
A
during the manufacturing process
B
under forward bias
C
under reverse bias
D
when temperature varies
31
The velocity of an oscillating charge as it moves to and fro along a wire is always
A
constant
B
zero
C
changing
D
infinite
32
Which one of following band is completely filled in case of conductors?
A
Conduction band
B
Fermi band
C
Valence band
D
Forbidden band
33
Which one of the following has the greatest energy gap?
A
insulator
B
conductor
C
semi conductor
D
any of above
34
The value of resistivity for insulator is of the order of
A
105 ohm metre
B
106 ohm metre
C
107 ohm metre
D
108 ohm metre
35
Thermions are
A
protons
B
positrons
C
electrons
D
photons
36
Hole is equivalent to
A
a negative charge
B
a positive charge
C
a neutral particle
D
an electron
37
Which one of the following is not a donor impurity?
A
antimony
B
phosphorus
C
aluminium
D
arsenic
38
Forward current through a semi conductor diode circuit is due to
A
minority carriers
B
majority carriers
C
holes
D
electrons
39
In the transistor schematic symbol, the arrow
A
is located on the emitter
B
is located on the base
C
is locate on the collector
D
points form north to south
40
In full wave rectification the output D.C. voltage across the load is obtained for
A
The positive half cycle of input A.C.
B
The negative half cycle of input A.C.
C
The complete cycle of input A.C.
D
All of the above.
41
The semiconductor diode can be used as a rectifier because _
A
It has low resistance to the current flow when forward biased & high resistance when reverse biased.
B
It has low resistance to the current flow when forward biased.
C
It has high resistance to the current flow when reverse biased
D
Its conductivity increases with rise of temperature.
42
In half-wave rectification the output D.C. voltages is obtained across the load for
A
The negative half cycle of A.C.
B
The positive half cycle of A.C.
C
The positive and negative half cycles
D
Either positive or negative half of A.C.
43
The device or circuit used for conversion of A.C. into D.C. is called
A
An amplifier.
B
A rectifier
C
Filtering circuit
D
Converter.
44
The device used for conversion of D.C. to A.C. is called
A
Converter
B
A rectifier
C
Inverter
D
Oscillator
45
The especially designed semiconductor diodes used as indicator lamps in electronic circuits are
A
The switch
B
The light emitting diode
C
The photo diodes
D
Solar cells.
46
The specially designed semi-conductor diodes used as fast counters in electronic circuits are
A
The light emitting diodes
B
Photo diodes
C
Photo voltaic cell
D
Solar cells.
47
The alternating voltage is an example of
A
A digital waveform
B
An analogue waveform
C
Discrete waveform
D
None at all
48
The rectangular voltage is an example of
A
An analogue waveform
B
Continuous wave form
C
Electronic waveform
D
A digital waveform
49
The operational amplifier is
A
A high gain amplifier
B
A high-power amplifier
C
A high resistance amplifier
D
A low resistance amplifier
50
In a half-wave rectifier the r.m.s. value of the A.C. component of the wave is
A
Equal to D.C. value
B
More than D.C. value
C
Less than D.C. value
D
Zero
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