question_answer 1)
Which of the following options is true?
A)
Moving electric charges produce magnetic fields. done
clear
B)
The phenomenon of generating current of e.m.f. by changing magnetic fields is called electromagnetic induction. done
clear
C)
Generators, transformers etc. works on the principle of electromagnetic induction. done
clear
D)
All of these. done
clear
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question_answer 2)
Electromagnetic induction is the:
A)
charging of a body with a positive charge done
clear
B)
production of current by relative motion between magnet and a coil done
clear
C)
rotation of the coil of an electric motor done
clear
D)
generation of magnetic field due to current carrying solenoid. done
clear
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question_answer 3)
In Faraday's experiment, current is not produced when
A)
the coil is moved and bar magnet is kept stationary done
clear
B)
the bar magnet is moved and the coil is kept stationary done
clear
C)
both coil and bar magnet are kept stationary done
clear
D)
both a, and b. done
clear
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question_answer 4)
In Faraday's experiment on electromagnetic induction, more deflection will be shown by galvanometer, when:
A)
magnet is in uniform motion towards the coil done
clear
B)
magnet is in uniform motion away from the coil done
clear
C)
magnet is in accelerated motion towards the coil done
clear
D)
magnet is at rest near the coil done
clear
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question_answer 5)
The diagram shows a coil of wire connected to a galvano meter A student has a magnet and an unmagnetised iron rod. How can an e.m.f. be induced across the coil?
A)
Holding the magnet inside the coil done
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B)
Holding the iron rod inside the coil done
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C)
Pushing the magnet into the coil done
clear
D)
Pushing the iron rod into the coil. done
clear
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question_answer 6)
The magnetic flux linked with a vector area \[\overrightarrow{A}\] in a uniform magnetic field \[\overrightarrow{B}\] is:
A)
\[\overrightarrow{B}\times \overrightarrow{A}\] done
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B)
\[\overrightarrow{B}\cdot \overrightarrow{A}\] done
clear
C)
both a, and b, done
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D)
None of these done
clear
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question_answer 7)
The flux linked with a closed coil held in a magnetic field is zero, when:
A)
the plane of coil is parallel to the magnetic field done
clear
B)
the plane of coil is perpendicular to the magnetic field done
clear
C)
the plane of coil is at an angle of \[60{}^\circ \] with the magnetic field done
clear
D)
the plane of coil is at an angle of \[120{}^\circ \] with the magnetic field done
clear
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question_answer 8)
S.I. unit of magnetic flux is:
A)
ampere-meter done
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B)
ampere \[{{m}^{2}}\] done
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C)
weber done
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D)
weber/\[{{m}^{2}}\] done
clear
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question_answer 9)
The dimensions of magnetic flux are:
A)
\[[M{{L}^{2}}{{T}^{-1}}{{A}^{-2}}]\] done
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B)
\[[M{{L}^{2}}{{T}^{-2}}{{A}^{-1}}]\] done
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C)
\[[ML{{T}^{-2}}{{A}^{-2}}]\] done
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D)
\[[M{{L}^{2}}{{T}^{-2}}{{A}^{-2}}]\] done
clear
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question_answer 10)
A circular loop of area \[0.05\text{ }{{m}^{2}}\] is kept parallel to a uniform magnetic field of 2 T. What is the flux linked with the loop?
A)
0.1 done
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B)
0.05 done
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C)
1 done
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D)
zero done
clear
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question_answer 11)
A rectangular loop of area \[20\text{ }cm\times 30\text{ }cm\] is placed in a magnetic field of 0.3 T, with its plane normal to the field. The flux linked with the coil is:
A)
0.009 Wb done
clear
B)
0.018 Wb done
clear
C)
zero done
clear
D)
0.06 Wb done
clear
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question_answer 12)
If area vector \[\overrightarrow{A}=3\widehat{i}+2\hat{j}+5\hat{k}\,{{m}^{2}}\], flux density \[\overrightarrow{B}=5\widehat{i}+10\hat{j}+6\hat{k}\,(Wb/{{m}^{2}})\]. The magnetic flux linked with the soil is:
A)
31 Wb done
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B)
65 Wb done
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C)
100 Wb done
clear
D)
90 Wb done
clear
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question_answer 13)
A circular disc of radius 0.2 m is placed in a uniform magnetic field of induction \[\frac{1}{\pi }\left( \frac{Wb}{{{m}^{2}}} \right)\] in such a way that its axis makes an angle of \[60{}^\circ \] with B. The magnetic flux linked with the disc is:
A)
0.02 Wb done
clear
B)
0.06 Wb done
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C)
0.08 Wb done
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D)
0.01 Wb done
clear
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question_answer 14)
A square of side L meters lies in the x-y plane in a region, where the magnetic field is given by \[\overrightarrow{B}={{B}_{0}}(2\widehat{i}+3\widehat{j}+4\widehat{k})T\]. where \[{{B}_{0}}\] is constant. The magnitude of flux passing through the square is: (NCERT exemplar)
A)
\[2{{B}_{0}}{{L}^{2}}Wb\] done
clear
B)
\[2{{B}_{0}}{{L}^{2}}Wb\] done
clear
C)
\[4{{B}_{0}}{{L}^{2}}Wb\] done
clear
D)
\[\sqrt{29}{{B}_{0}}{{L}^{2}}Wb\] done
clear
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question_answer 15)
A Loop, made of straight edges has six corners at A(0, 0, 0), B(L, 0, 0) C(L, L, 0), D(0, L, 0). E(0, L, L) and F(0, 0, L). A magnetic field \[\overrightarrow{B}={{B}_{0}}(\widehat{i}+\widehat{k})T\] is present in the region. The flux passing through the loop ABCDEFA (in that order) is: (NCERT EXEMPLAR)
A)
\[{{B}_{0}}{{L}^{2}}Wb\] done
clear
B)
\[2{{B}_{0}}{{L}^{2}}Wb\] done
clear
C)
\[\sqrt{2}{{B}_{0}}{{L}^{2}}Wb\] done
clear
D)
\[4{{B}_{0}}{{L}^{2}}Wb\] done
clear
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question_answer 16)
A graph between induced current and time is shown below, for a coil of resistance \[5\,\Omega \], when it is kept in a changing magnetic flux. The magnitude of change in flux through the coil (in weber) is:
A)
6 Wb done
clear
B)
3 Wb done
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C)
4 Wb done
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D)
2 Wb done
clear
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question_answer 17)
Due to relative motion of a magnet with respect to a coil, an emf is induced in the coil, identify the principle involved:
A)
Ampere's circuital law done
clear
B)
Faraday's law done
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C)
Gauss law done
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D)
Biot-Savart law done
clear
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question_answer 18)
Induced emf in the coil depend upon:
A)
conductivity of coil done
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B)
amount flux done
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C)
rate of change of linked flux done
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D)
resistance coil done
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question_answer 19)
The magnetic flux linked with a coil at any instant is given by \[\phi =(5{{t}^{3}}-50t+200)Wb\]. The magnitude of emf induced in the coil at t = 2s is:
A)
40 V done
clear
B)
140 V done
clear
C)
10 V done
clear
D)
300 V done
clear
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question_answer 20)
The magnetic flux linked with a coil satisfies the relation \[\phi =(4{{t}^{2}}+6t+9)Wb\] where t is the time in second. The emf induced in the coil at t = 2 s is:
A)
22 V done
clear
B)
18 V done
clear
C)
16 V done
clear
D)
40 V done
clear
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question_answer 21)
A conducting coil is held stationary in a non-uniform magnetic field. The emf induced in the coil is:
A)
maximum done
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B)
minimum done
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C)
zero done
clear
D)
Blv done
clear
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question_answer 22)
A small piece of metal wire is dragged across the gap between the poles of a magnet in 0.4 s. If change in magnetic flux in the wire is \[8\times {{10}^{-4}}Wb\], then e.m.f. induced in the wire is:
A)
\[8\times {{10}^{-3}}V\] done
clear
B)
\[6\times {{10}^{-3}}V\] done
clear
C)
\[4\times {{10}^{-3}}V\] done
clear
D)
\[2\times {{10}^{-3}}V\] done
clear
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question_answer 23)
A coil having an area \[{{A}_{0}}\] is placed in a magnetic field which changes from \[{{B}_{0}}\] to \[4{{\underline{B}}_{0}}\] in a time interval t. the e.m.f. induced in the coil will be:
A)
\[\frac{3{{A}_{0}}{{B}_{0}}}{t}\] done
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B)
\[\frac{4{{A}_{0}}{{B}_{0}}}{t}\] done
clear
C)
\[\frac{3{{B}_{0}}}{{{A}_{0}}t}\] done
clear
D)
\[\frac{4{{B}_{0}}}{{{A}_{0}}t}\] done
clear
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question_answer 24)
A coil of area \[0.4\text{ }{{m}^{2}}\] has 100 turns. A magnetic field of \[0.04\text{ }Wb\text{ }{{\text{m}}^{-2}}\] is acting normal to the coil surface. If this magnetic field is reduced to zero in 0.01 s, then the induced emf in the coil is:
A)
160 V done
clear
B)
250 V done
clear
C)
270 V done
clear
D)
320 V done
clear
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question_answer 25)
Whenever there is a change in the magnetic flux linked with a closed circuit, an emf and a current are induced in the circuit. This statement is referred to as:
A)
Lenz's law done
clear
B)
Faraday's second law of electromagnetic induction done
clear
C)
(c) Faraday's first law of electromagnetic induction done
clear
D)
Laplace's law done
clear
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question_answer 26)
Unit of induced emf is:
A)
ampere done
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B)
volt done
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C)
joule done
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D)
electron volt done
clear
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question_answer 27)
A, B and C are the three coils of conductor having different number of turns, wound around a soft iron ring as shown in the figure. Ends of coils B and C are connected to the galvanometers. The observation that can be made when ends of coil A are connected to an A.C. source is:
A)
Same electric current is induced in B and C done
clear
B)
No electric current is induced in B and C done
clear
C)
Induced electric current is more in B than in C done
clear
D)
induced electric current is less in B than in C done
clear
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question_answer 28)
A rectangular coil of 100 turns and size \[0.1\text{ }m\times 0.05\text{ }m\] is placed perpendicular to a magnetic field of 0.1 T. If the field drops to 0.05 T in 0.05 second, the magnitude of the e.m.f. induced in the coil is:
A)
2 V done
clear
B)
3V done
clear
C)
0.5 V done
clear
D)
6 V done
clear
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question_answer 29)
The magnetic flux through a coil perpendicular to its plane and directed into paper is varying according to the relation \[\phi =(2{{t}^{2}}+4t+6)mWb\]. The emf induced in the loop at \[t=4s\] is:
A)
0.12 V done
clear
B)
2.4 V done
clear
C)
0.02 V done
clear
D)
1.2 V done
clear
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question_answer 30)
A long solenoid with 10 turns per cm has a small loop of area \[\text{3 }c{{m}^{2}}\] placed inside, normal to the axis of the solenoid. If the current carried by the solenoid changes steadily from 2 A to 4 A in 0.2s, what is the induced voltage in the loop, while the current in changing?
A)
\[4.2\times {{10}^{-8}}V\] done
clear
B)
\[2.8\times {{10}^{-8}}V\] done
clear
C)
\[7.3\times {{10}^{-6}}V\] done
clear
D)
\[3.8\times {{10}^{-6}}V\] done
clear
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question_answer 31)
The phase different between the flux linked with a coil rotating in a uniform magnetic field and induced emf produced in it is:
A)
\[\frac{\pi }{4}\] done
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B)
\[\frac{\pi }{2}\] done
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C)
\[\frac{-\pi }{6}\] done
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D)
\[\pi \] done
clear
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question_answer 32)
If the instantaneous magnetic flux and induced emf produced in a coil is \[\phi \] and \[\varepsilon \] respectively, then according to Faraday's law of electromagnetic induction:
A)
\[\varepsilon \] must be zero if \[\phi =0\] and changing done
clear
B)
\[\varepsilon \ne 0\] and \[\phi =0\] done
clear
C)
\[\varepsilon =0\] then \[\phi \] must be zero done
clear
D)
\[\varepsilon \ne 0\] if \[\phi \] is changing done
clear
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question_answer 33)
A square loop side 12 cm and resistance \[0.60\,\Omega \]. is placed vertically in the east-west plane. A uniform magnetic field of 0.10 T is set up across the plane in north-east direction. The magnetic field is decreased to zero in 0.6 s at a steady rate. The magnitude of current during this time interval is:
A)
\[1.42\times {{10}^{-3}}A\] done
clear
B)
\[2.67\times {{10}^{-3}}A\] done
clear
C)
\[3.41\times {{10}^{-3}}A\] done
clear
D)
\[4.21\times {{10}^{-3}}A\] done
clear
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question_answer 34)
According to Lenz's law of electromagnetic induction:
A)
the induced emf is not in the direction opposing the change in magnetic flux done
clear
B)
the relative motion between the coil and magnet produces change in magnetic flux done
clear
C)
only the magnet should be moved towards coil done
clear
D)
only the coil should be moved towards magnet done
clear
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question_answer 35)
Lenzs law is consequence of the law of conservation of:
A)
momentum done
clear
B)
mass done
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C)
charge done
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D)
energy done
clear
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question_answer 36)
A bar magnet is dropped between a current carrying coil. What would be its acceleration?
A)
g downwards done
clear
B)
Greater than g downwards done
clear
C)
Less than g downwards done
clear
D)
Bar will be stationary done
clear
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question_answer 37)
A metallic ring is attached with the wall of a room. When the north pole of a magnet is brought near it, the induced current in the ring will be:
A)
first clockwise than anticlockwise done
clear
B)
in clockwise direction done
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C)
in anticlockwise direction done
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D)
first anticlockwise then clockwise done
clear
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question_answer 38)
Which of the following is found using Lenz's law?
A)
induced emf done
clear
B)
induced current done
clear
C)
direction of induced emf done
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D)
direction of alternating current done
clear
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question_answer 39)
There is a uniform magnetic field directed perpendicular and into the plane of the paper An irregular shaped conducting loop is slowly changing into a circular loop in the plane of the paper. Then:
A)
current is induced in the loop in the anti-clockwise direction done
clear
B)
current is induced in the loop in the clockwise direction done
clear
C)
ac is induced in the loop. done
clear
D)
no current is induced in the loop. done
clear
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question_answer 40)
In the given figure, current from A to B in the straight wire is decreasing. The direction of induced current in the loop is:
A)
clockwise done
clear
B)
anticlockwise done
clear
C)
changing done
clear
D)
nothing can be said done
clear
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question_answer 41)
The variation of induced emf \[(\varepsilon )\] with time \[(t)\] in a coil if a short bar magnet is moved along its axis with a constant velocity is best represented as:
A)
B)
C)
D)
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question_answer 42)
A cylindrical bar magnet is rotated about its axis as shown in figure. A wire is connected from the axis and is made to touch the cylindrical surface through a contact Then: (NCERT EXEMPLAR)
A)
a direct current flows in through the ammeter A. done
clear
B)
no current flows through the ammeter A. done
clear
C)
an alternating sinusoidal current flows through the ammeter A with a time period, \[T=\frac{2\pi }{\omega }\]. done
clear
D)
a time varying non-sinusoidal current flows through the ammeter A. done
clear
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question_answer 43)
There are two coils A and B as shown in the figure. A current starts flowing in B as shown, when A is moved towards B and stops when A stops moving. The current in A is counter clockwise, B is kept stationary when A moves. We can infer that: (NCERT EXEMPLAR)
A)
there is a constant current in the clockwise direction of A. done
clear
B)
there is a varying current in A. done
clear
C)
there is no current in A done
clear
D)
there is a constant current in the counter-clockwise direction in A. done
clear
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question_answer 44)
Same as problem 43 except the coil A is made to rotate about a vertical axis. No current flows in B if A is at rest. The current in coil A when the current in B (at t = 0) is counter-clockwise and the coil A is as shown at this instant, t - 0, is: (NCERT EXEMPLAR)
A)
constant current clockwise done
clear
B)
varying current clockwise done
clear
C)
varying current counter-clockwise done
clear
D)
constant current counter-clockwise done
clear
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question_answer 45)
Two different loops are concentric and lie in the same plane. The current in the outer loop is clockwise and increasing with time. The induced current in the inner loop, is:
A)
clockwise done
clear
B)
zero done
clear
C)
counter-clockwise done
clear
D)
in a direction that depends on the ratio of the loop radii done
clear
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question_answer 46)
A)
A-p B-q C-r done
clear
B)
A-r B-q C-p done
clear
C)
A-p B-r C-q done
clear
D)
A-r B-p C-q done
clear
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question_answer 47)
A conducting rod of length l is falling with a constant velocity v perpendicular to a uniform magnetic field B. A potential difference between its two ends wil be:
A)
2 Blv done
clear
B)
Blv done
clear
C)
\[\frac{1}{2}Blv\] done
clear
D)
\[{{B}^{2}}{{l}^{2}}{{v}^{2}}\] done
clear
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question_answer 48)
A straight line conductor of length 0.4 m is moved with a speed of 7 m/s perpendicular to a magnetic field of intensity \[0.9\text{ }Wb/{{m}^{2}}\]. The induced e.m.f across the conductor is:
A)
5.04 V done
clear
B)
1.26 V done
clear
C)
2.52 V done
clear
D)
25.2 V done
clear
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question_answer 49)
A wire of length 50 cm moves with a velocity of 300 m/min, perpendicular to a magnetic field. If the emf induced in the wire is 2 V, then the magnitude of the field (in tesla) is:
A)
2 done
clear
B)
5 done
clear
C)
0.4 done
clear
D)
0.8 done
clear
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question_answer 50)
An aeroplane having a wing span of 35 m flies due north with the speed of 90 m/s. If the magnetic field \[B=4\times {{10}^{-5}}T\] then, the potential difference developed between the tip of the wings is:
A)
1.26 V done
clear
B)
1.03 V done
clear
C)
12.6 V done
clear
D)
0.126 V done
clear
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question_answer 51)
A metallic square loop ABCD is moving in its own plane with velocity v in a uniform magnetic field perpendicular to its plane as shown in figure. An electric field is induced
A)
in AD, but not in BC done
clear
B)
in BC, but not in AD done
clear
C)
neither in AD nor in BC done
clear
D)
in both AD and BC done
clear
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question_answer 52)
A conductor is moving with the velocity v in the magnetic field and let l be the induced current. If the velocity of conductor becomes double, the induced current will be:
A)
0.5 l done
clear
B)
1.5 l done
clear
C)
2 l done
clear
D)
2.5 l done
clear
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question_answer 53)
A rectangular loop of side 6 cm and 2 cm with a small cut is moving out of a region of uniform magnetic field of magnitude 0.4 T directed normal to the loop. The voltage developed across the cut if velocity of loop is \[2\text{ }cm\text{ }{{s}^{-1}}\] in a direction normal to the longer side is:
A)
\[3.8\times {{10}^{-4}}V\] done
clear
B)
\[4.8\times {{10}^{-4}}V\] done
clear
C)
\[2.2\times {{10}^{-2}}V\] done
clear
D)
\[3.2\times {{10}^{-2}}V\] done
clear
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question_answer 54)
In the question number 53, if velocity is normal in the shorter side then the voltage developed is:
A)
\[2.3\times {{10}^{-4}}V\] done
clear
B)
\[2.4\times {{10}^{-2}}V\] done
clear
C)
\[4.8\times {{10}^{-2}}V\] done
clear
D)
\[1.6\times {{10}^{-4}}V\] done
clear
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question_answer 55)
A jet plane is travelling west at the speed of \[1800\text{ }km\text{ }{{h}^{-1}}\]. The potential difference developed between the ends of the wing having a span of 25 m, if the earth's magnetic field at the location has a magnitude of \[5\times {{10}^{-4}}T\] and the dip angle is \[30{}^\circ \] is:
A)
\[4.125\,\,V\] done
clear
B)
\[3.125\,\,V\] done
clear
C)
\[2.225\text{ }V\] done
clear
D)
\[3.8\text{ }V\] done
clear
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question_answer 56)
A copper rod of Length I rotates about its end with angular velocity \[\omega \] in a uniform magnetic field B. The emf developed between the ends of the rod if the field is normal to the plane of rotation is:
A)
\[B\omega {{l}^{2}}\] done
clear
B)
\[\frac{1}{2}B\omega {{l}^{2}}\] done
clear
C)
\[2\,B\omega {{l}^{2}}\] done
clear
D)
\[\frac{1}{4}\,B\omega {{l}^{2}}\] done
clear
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question_answer 57)
A 2 m Long metallic rod rotates with an angular frequency of \[200\text{ }rad\text{ }{{s}^{-1}}\] about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic ring. A constant magnetic field of 0.5 T parallel to the axis exists everywhere. The emf developed between the centre and the ring is:
A)
100 V done
clear
B)
200 V done
clear
C)
300 V done
clear
D)
400 V done
clear
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question_answer 58)
A metal conductor of length 1 m rotates vertically about one of its ends with an angular velocity 5 rad \[{{s}^{-1}}\]. If the horizontal component of earth's magnetic field is \[0.2\times {{10}^{-4}}T\], then the emf developed between the end of the conductor is:
A)
\[5\mu V\] done
clear
B)
5 mV done
clear
C)
\[50\mu V\] done
clear
D)
50 mV done
clear
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question_answer 59)
A wheel with 20 metallic spokes each of length 0.5m long is rotated with a speed of 120 revolution per minute in a plane, normal to the horizontal component of earth magnetic field H at a place. If \[H=0.4\times {{10}^{-4}}T\] at the place, then induced emf between the axle and the rim of the wheel is:
A)
\[6.28\times {{10}^{-5}}V\] done
clear
B)
\[3.14\times {{10}^{-5}}V\] done
clear
C)
\[1.256\times {{10}^{-5}}V\] done
clear
D)
\[1.57\times {{10}^{-5}}V\] done
clear
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question_answer 60)
A circular copper disc 10 cm in diameter rotates 1800 revolution per minute about an axis through its centre and at right angles to disc. A uniform field of \[1\text{ }Wb\text{ }{{m}^{-2}}\] is perpendicular to disc. What potential difference is developed between the axis of the disc and the rim?
A)
0.023 V done
clear
B)
0.23 V done
clear
C)
23 V done
clear
D)
230 V done
clear
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question_answer 61)
A semicircle Loop PQ of radius R is moved with velocity V in transverse magnetic field as shown in figure. The value of induced emf at the end of loop is:
A)
\[2BvR\] done
clear
B)
BvR done
clear
C)
\[\frac{1}{2}BvR\] done
clear
D)
\[{{B}^{2}}{{v}^{2}}{{R}^{2}}\] done
clear
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question_answer 62)
If given arrangement is moving towards left with speed v, then potential difference between B and D and current in the loop are respectively.
A)
BvR and non-zero done
clear
B)
2BvR and zero done
clear
C)
4BvR and non-zero done
clear
D)
4BvR and zero done
clear
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question_answer 63)
A conductor square loop of side L and resistance R moves in its plane with a uniform velocity v perpendicular to one of its sides. A magnetic induction B constant in time and space, pointing perpendicular and into the plane of the loop exists everywhere. The current induced in the loop is:
A)
\[\frac{Blv}{R}\text{clockwise}\] done
clear
B)
\[\frac{Blv}{R}\text{anti}\,\text{clockwise}\] done
clear
C)
\[\frac{2Blv}{R}\text{anti}\,\text{clockwise}\] done
clear
D)
zero done
clear
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question_answer 64)
A conducting square loop of side L and resistance R moves out of a uniform magnetic field B with a uniform velocity v as shown in the figure. The induced current in the loop is:
A)
zero done
clear
B)
BRv done
clear
C)
BvL/R done
clear
D)
BvL done
clear
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question_answer 65)
A square loop of side l, resistance R is placed in a uniform magnetic field B acting normally to the plane of the loop. If we attempt to pull it out of the field with a constant velocity v, then the power needed is:
A)
\[BRlv\] done
clear
B)
\[\frac{{{B}^{2}}{{l}^{2}}{{v}^{2}}}{R}\] done
clear
C)
\[\frac{B{{l}^{2}}{{v}^{2}}}{R}\] done
clear
D)
\[\frac{Bvl}{R}\] done
clear
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question_answer 66)
The magnetic flux through a circuit of resistance R changes by an amount \[\Delta \,\phi \] in time \[\Delta \,t\], then the total quantity of electric charge Q, which passing during this time through any point of the circuit is given by:
A)
\[Q=\frac{\Delta \,\phi }{\Delta \,t}\] done
clear
B)
\[Q=\frac{\Delta \,\phi }{\Delta \,t}\times R\] done
clear
C)
\[Q=-\frac{\Delta \,\phi }{\Delta \,t}+R\] done
clear
D)
\[Q=\frac{\Delta \,\phi }{R}\] done
clear
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question_answer 67)
In a circuit with a coil of resistance 2 ohms, the magnetic flux changes from 2.0 Wb to 10.0 Wb in 0.2 second. The charge that flows in the coil during this time is:
A)
5.0 coulomb done
clear
B)
4.0 coulomb done
clear
C)
1.0 coulomb done
clear
D)
0.8 coulomb done
clear
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question_answer 68)
In a magnetic field 0.05 T, area of coil changes from \[101\text{ }c{{m}^{2}}\] to \[100\text{ }c{{m}^{2}}\] without changing the resistance which is \[2\,\Omega \]. The amount of charge that flows during this period is:
A)
\[{{10}^{-6}}C\] done
clear
B)
\[2\times {{10}^{-6}}C\] done
clear
C)
\[8\times {{10}^{-6}}C\] done
clear
D)
\[2.5\times {{10}^{-6}}C\] done
clear
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question_answer 69)
Eddy currents are produced, when
A)
a circular coil is placed in a magnetic field done
clear
B)
a metal is kept in a varying magnetic field done
clear
C)
a metal is kept in a steady magnetic field done
clear
D)
current is passes through a circular coil done
clear
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question_answer 70)
Which of the following is true in context of Eddy currents?
A)
By Lenz's law, an eddy current creates a magnetic field that opposes the magnetic field that created it done
clear
B)
Eddy currents are loops of electrical current induced within conductors by a changing magnetic field in the conductor due to Faraday's law of induction done
clear
C)
Eddy currents are a cause-of energy loss in AC inductors, transformers, generators etc. done
clear
D)
All of the above done
clear
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question_answer 71)
Oscillating metallic pendulum in a uniform magnetic field directed perpendicular to the plane of oscillation:
A)
slows down done
clear
B)
becomes faster done
clear
C)
remains unaffected done
clear
D)
oscillates with changing frequency done
clear
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question_answer 72)
A coil is suspended in a uniform magnetic field. When a current is passed through the coil it starts oscillating. But when an aluminium plate is placed near the coil, it stops. This is due to:
A)
development of air current when the plate is placed done
clear
B)
induction of electrical charge on the plate done
clear
C)
shielding of magnetic lines of force as aluminium is a paramagnetic material. done
clear
D)
electromagnetic induction in the aluminium plate giving rise to electromagnetic damping done
clear
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question_answer 73)
Eddy current can be minimised by using:
A)
thick wires done
clear
B)
thin sheets of metal done
clear
C)
thick sheets done
clear
D)
laminated sheets done
clear
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question_answer 74)
Induction furnace is based on the principle of:
A)
self induction done
clear
B)
mutual induction done
clear
C)
eddy current done
clear
D)
None of these done
clear
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question_answer 75)
Which of the following does not use the application of eddy current?
A)
Electric power meters done
clear
B)
Induction furnace done
clear
C)
LED lights done
clear
D)
Magnetic brakes in trains done
clear
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question_answer 76)
Eddy currents do not cause:
A)
heating done
clear
B)
loss of energy done
clear
C)
sparking done
clear
D)
damping done
clear
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question_answer 77)
Which of the following will not increase the size and effect of eddy current?
A)
thinner material done
clear
B)
low resistivity materials done
clear
C)
strong magnetic field done
clear
D)
thicker material done
clear
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question_answer 78)
How can electromagnetic damping be increased?
A)
increasing the magnetic density done
clear
B)
reduce viscosity done
clear
C)
winding the coil on the aluminum frame done
clear
D)
increase the temperature of the coil done
clear
View Solution play_arrow
question_answer 79)
The SI unit of inductance, can be written as:
A)
volt - ampere/second done
clear
B)
\[\text{joule/(ampere}{{\text{)}}^{\text{2}}}\] done
clear
C)
\[ohm-{{(second)}^{2}}\] done
clear
D)
volt-second/ampere done
clear
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question_answer 80)
The coefficient of mutual inductance of two coils depends on:
A)
medium between the coils done
clear
B)
distance between the two coils done
clear
C)
orientation of the two coils done
clear
D)
All of these done
clear
View Solution play_arrow
question_answer 81)
Two circular coils can be arranged if any of three situations as shown in the figure. Their mutual inductance will be:
A)
maximum in situation (i) done
clear
B)
maximum in situation (ii) done
clear
C)
maximum in situation (iii) done
clear
D)
same in all situations done
clear
View Solution play_arrow
question_answer 82)
Two coils A and B are separated by a certain distance. If a current of 4 A flows through A a magnetic flux of \[{{10}^{-3}}Wb\] passes through B (no current through B). If no current passes through A and a current of 2A passes through B, then the flux A is:
A)
\[5\times {{10}^{-3}}Wb\] done
clear
B)
\[4\times {{10}^{-4}}Wb\] done
clear
C)
\[5\times {{10}^{-4}}Wb\] done
clear
D)
\[2\times {{10}^{-4}}Wb\] done
clear
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question_answer 83)
A short solenoid of radius a, number of turns per unit length \[{{n}_{1}}\] and length L is kept coaxially inside a very long solenoid of radius b, number of turns per unit length \[{{n}_{2}}\]. What is the mutual inductances of the system?
A)
\[{{\mu }_{0}}\pi {{b}^{2}}{{n}_{1}}{{n}_{2}}L\] done
clear
B)
\[{{\mu }_{0}}\pi {{a}^{2}}{{n}_{1}}{{n}_{2}}{{L}^{2}}\] done
clear
C)
\[{{\mu }_{0}}\pi {{a}^{2}}{{n}_{1}}{{n}_{2}}L\] done
clear
D)
\[{{\mu }_{0}}\pi {{b}^{2}}{{n}_{1}}{{n}_{2}}{{L}^{2}}\] done
clear
View Solution play_arrow
question_answer 84)
If numbers of turns in primary and secondary coils is increased to two times each, the mutual inductances:
A)
becomes 4 times done
clear
B)
becomes 2 times done
clear
C)
becomes \[\frac{1}{4}\] times done
clear
D)
remain unchanged done
clear
View Solution play_arrow
question_answer 85)
A 2 m Long solenoid with diameter 2 cm and 2000 turns has a secondary coil of 1000 turns would closely near its midpoint. The mutual inductance between the two coils is:
A)
\[2.4\times {{10}^{-4}}H\] done
clear
B)
\[3.9\times {{10}^{-4}}H\] done
clear
C)
\[1.28\times {{10}^{-3}}H\] done
clear
D)
\[3.14\times {{10}^{-3}}H\] done
clear
View Solution play_arrow
question_answer 86)
Two coils A and B having turns 300 and 600 respectively are placed near each other. On passing a current of 3A in A the flux linked with 'A is \[1.2\times {{10}^{-4}}Wb\] and with B it is \[9\times {{10}^{-5}}Wb\]. The mutual induction of the system is:
A)
\[2.4\times {{10}^{-4}}H\] done
clear
B)
\[0.4\times {{10}^{-5}}H\] done
clear
C)
\[8\times {{10}^{-5}}H\] done
clear
D)
\[2\times {{10}^{-5}}H\] done
clear
View Solution play_arrow
question_answer 87)
Two coils X and Y are placed in a circuit such that a current changes by 3A in coil X and magnetic flux change of 1.2 Wb occurs in Y. The value of mutual inductance of the coils is:
A)
0.2 H done
clear
B)
0.4 H done
clear
C)
3.6 H done
clear
D)
0.6 H done
clear
View Solution play_arrow
question_answer 88)
In mutual induction: A: When current in one coil increases, induced current in neighbouring coil flows in the opposite direction. B: When current in one coil decreases, induced current in neighbouring coil flows in the opposite direction.
A)
A is true B is false done
clear
B)
A and B are false done
clear
C)
A and B are true done
clear
D)
A is false B is true done
clear
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question_answer 89)
For a current carrying inductor, emf associated is 20 mV. Now, current through it changes from 6A to 2A in 2s. The coefficient of mutual inductance is:
A)
1 mH done
clear
B)
20 mH done
clear
C)
2 mH done
clear
D)
10 mH done
clear
View Solution play_arrow
question_answer 90)
Two conducting circular loops of radii \[{{R}_{1}}\] and \[{{R}_{2}}\] are placed in the same plane with their centres coinciding. If \[{{R}_{1}}>{{R}_{2}}\], the mutual inductance M between them will be directly proportional to:
A)
\[\frac{{{R}_{1}}}{{{R}_{2}}}\] done
clear
B)
\[\frac{{{R}_{2}}}{{{R}_{1}}}\] done
clear
C)
\[\frac{R_{1}^{2}}{{{R}_{2}}}\] done
clear
D)
\[\frac{R_{2}^{2}}{{{R}_{1}}}\] done
clear
View Solution play_arrow
question_answer 91)
Which of the following units denotes the dimension \[\frac{M{{L}^{2}}}{{{Q}^{2}}}\], where Q denotes the electric charge?
A)
\[\text{weber/}{{\text{m}}^{\text{2}}}\] done
clear
B)
Henry(H) done
clear
C)
\[H/{{m}^{2}}\] done
clear
D)
weber done
clear
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question_answer 92)
The value of coefficient of mutual induction for the arrangement of two coils shown in the figure will be:
A)
Zero done
clear
B)
maximum done
clear
C)
positive done
clear
D)
negative done
clear
View Solution play_arrow
question_answer 93)
The physical quantity which is measured in the unit of Wb \[{{A}^{-1}}\] is:
A)
self inductance done
clear
B)
mutual inductance done
clear
C)
magnetic flux done
clear
D)
Both a. and b. done
clear
View Solution play_arrow
question_answer 94)
The self inductance of a coil is proportional to:
A)
its length done
clear
B)
the number of turns done
clear
C)
the resistance of soil done
clear
D)
the square of the number of turns done
clear
View Solution play_arrow
question_answer 95)
The self inductance is independent of:
A)
number of turns done
clear
B)
medium done
clear
C)
length done
clear
D)
current done
clear
View Solution play_arrow
question_answer 96)
If N is the number of turns in a coil, then the value of self-inductance varies as:
A)
N done
clear
B)
\[{{N}^{2}}\] done
clear
C)
\[{{N}^{-2}}\] done
clear
D)
\[{{N}^{3}}\] done
clear
View Solution play_arrow
question_answer 97)
If coil is open, then L and R become:
A)
\[\infty ,\,\,0\] done
clear
B)
\[0,\,\,\infty \] done
clear
C)
\[\infty ,\,\,\infty \] done
clear
D)
0, 0 done
clear
View Solution play_arrow
question_answer 98)
When the number of turns of the coil is increased twice and the length is reduced by 4, what will be the self inductance of the coil?
A)
increased by 4 done
clear
B)
decreased by 4 done
clear
C)
remain the same done
clear
D)
increased by 2 done
clear
View Solution play_arrow
question_answer 99)
The self inductance L of a solenoid of length l and area of cross-section A, with a fixed number of turns N increases as: (NCERT EXEMPLAR)
A)
l and A increases done
clear
B)
l decreases and A increases done
clear
C)
l increases and A decreases done
clear
D)
Both l and A decreases done
clear
View Solution play_arrow
question_answer 100)
The number of turns and length of the solenoid are both doubled, keeping area of cross-section of the solenoid same. Then self-inductance of the coil will be:
A)
halved done
clear
B)
doubled done
clear
C)
1/4 times the original value done
clear
D)
unaffected done
clear
View Solution play_arrow
question_answer 101)
The self inductance of a long solenoid cannot be increased by:
A)
increasing its area of cross section done
clear
B)
decreasing its length done
clear
C)
increasing the current through it done
clear
D)
increasing the number of turns in it done
clear
View Solution play_arrow
question_answer 102)
When the rate of change of current is unity, the induced emf is equal to:
A)
thickness of coil done
clear
B)
number of turns in coil done
clear
C)
coefficient of self inductance done
clear
D)
total flux linked with coil done
clear
View Solution play_arrow
question_answer 103)
When the current changes from + 2 A to - 2 A in 0.05 s, an emf of 8V as induced in a coil. The coefficient of self-induction of the coil is:
A)
0.2 H done
clear
B)
0.4 H done
clear
C)
0.8 H done
clear
D)
0.1 H done
clear
View Solution play_arrow
question_answer 104)
Two solenoids of equal number of turns have their lengths and the radii in the same radio \[1:2\]. The ratio of their self inductances will be:
A)
\[1:2\] done
clear
B)
\[2:1\] done
clear
C)
\[1:1\] done
clear
D)
\[1:4\] done
clear
View Solution play_arrow
question_answer 105)
What would be the coefficient of self-inductance of a coil of 100 turns, if 5A current flows through it? (Given that, magnetic flux \[=5\times {{10}^{3}}\] Maxwell)
A)
\[0.5\times {{10}^{-3}}H\] done
clear
B)
\[2\times {{10}^{-3}}H\] done
clear
C)
Zero done
clear
D)
\[{{10}^{-3}}H\] done
clear
View Solution play_arrow
question_answer 106)
The self inductance of an inductor coil having 100 turns is 20 mH. The magnetic flux through the cross-section of the coil corresponding to a current of 4 mA is:
A)
\[2\times {{10}^{-5}}Wb\] done
clear
B)
\[4\times {{10}^{-7}}Wb\] done
clear
C)
\[8\times {{10}^{-7}}Wb\] done
clear
D)
\[8\times {{10}^{-5}}Wb\] done
clear
View Solution play_arrow
question_answer 107)
In an inductor of self inductance L = 2 mH, current changes with time according to relation, \[l={{t}^{2}}{{e}^{-t}}\]. At what time emf is zero.
A)
4s done
clear
B)
3s done
clear
C)
2s done
clear
D)
1s done
clear
View Solution play_arrow
question_answer 108)
The equivalent quantity of mass in electricity is:
A)
current done
clear
B)
self inductance done
clear
C)
potential done
clear
D)
charge done
clear
View Solution play_arrow
question_answer 109)
If the self inductance of 500 turns coils is 125 mH, then the self inductance of the similar coil of 800 turns is:
A)
48.8 mH done
clear
B)
200 mH done
clear
C)
290 mH done
clear
D)
320 mH done
clear
View Solution play_arrow
question_answer 110)
A 10V better connected to \[5\Omega \] resistance coil having inductance 10 H through a switch drives a constant current in the circuit. The switch is suddenly opened and the time taken to open it is 2 ms. The average emf induced across the coil is:
A)
\[4\times {{10}^{4}}V\] done
clear
B)
\[2\times {{10}^{4}}V\] done
clear
C)
\[2\times {{10}^{2}}V\] done
clear
D)
\[1\times {{10}^{4}}V\] done
clear
View Solution play_arrow
question_answer 111)
A solenoid 30 cm long is made by winding 2000 loops of wire on an iron rod whose cross-section is \[1.5\text{ }c{{m}^{2}}\]. If the relative permeability of iron is 6000. What is the self-inductance of the solenoid?
A)
25 H done
clear
B)
5 H done
clear
C)
15 H done
clear
D)
35 H done
clear
View Solution play_arrow
question_answer 112)
The energy stored in an inductor of self inductance L henry carrying a current of l ampere is:
A)
\[\frac{1}{2}{{L}^{2}}l\] done
clear
B)
\[\frac{1}{2}L{{l}^{2}}\] done
clear
C)
\[L{{l}^{2}}\] done
clear
D)
\[{{L}^{2}}l\] done
clear
View Solution play_arrow
question_answer 113)
A 200 mH coil carries a current of 2 A. Energy stored in its magnetic field is:
A)
0.5 J done
clear
B)
0.4 J done
clear
C)
1 J done
clear
D)
0.1 J done
clear
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question_answer 114)
By a change of current from 5 A to 10 A in 0.1 s the self induced emf is 10 V. The change in the energy of the magnetic field of a coil will be:
A)
5 J done
clear
B)
6 J done
clear
C)
7.5 J done
clear
D)
9 J done
clear
View Solution play_arrow
question_answer 115)
Two coils of self-inductance 4 mH and 9 mH are placed so close together that the effective flux in one coil is completely linked with the other. The natural inductance between these coils are:
A)
16m H done
clear
B)
10 mH done
clear
C)
26 mH done
clear
D)
6 mH done
clear
View Solution play_arrow