12th Class Physics Electro Magnetic Induction Question Bank

done MCQ - Electromagnetic Induction Total Questions - 115

• question_answer1)
  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
  View Solution play_arrow

• question_answer2)
  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_answer3)
  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
  View Solution play_arrow

• question_answer4)
  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
  View Solution play_arrow

• question_answer5)
  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 clear
  B)
  Holding the iron rod inside the coil                       done clear
  C)
  Pushing the magnet into the coil                       done clear
  D)
  Pushing the iron rod into the coil. done clear
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• question_answer6)
                      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 clear
  B)
  \[\overrightarrow{B}\cdot \overrightarrow{A}\] done clear
  C)
  both a, and b,                done clear
  D)
  None of these                done clear
  View Solution play_arrow

• question_answer7)
  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_answer8)
                                                                   S.I. unit of magnetic flux is:
  A)
  ampere-meter                 done clear
  B)
  ampere \[{{m}^{2}}\] done clear
  C)
  weber                done clear
  D)
  weber/\[{{m}^{2}}\] done clear
  View Solution play_arrow

• question_answer9)
    The dimensions of magnetic flux are:
  A)
  \[[M{{L}^{2}}{{T}^{-1}}{{A}^{-2}}]\]                     done clear
  B)
  \[[M{{L}^{2}}{{T}^{-2}}{{A}^{-1}}]\] done clear
  C)
  \[[ML{{T}^{-2}}{{A}^{-2}}]\]                        done clear
  D)
  \[[M{{L}^{2}}{{T}^{-2}}{{A}^{-2}}]\] done clear
  View Solution play_arrow

• question_answer10)
  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 clear
  B)
  0.05     done clear
  C)
  1                                  done clear
  D)
  zero           done clear
  View Solution play_arrow

• question_answer11)
  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
  View Solution play_arrow

• question_answer12)
  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 clear
  B)
  65 Wb  done clear
  C)
  100 Wb                         done clear
  D)
  90 Wb done clear
  View Solution play_arrow

• question_answer13)
  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 clear
  C)
  0.08 Wb                        done clear
  D)
  0.01 Wb done clear
  View Solution play_arrow

• question_answer14)
  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
  View Solution play_arrow

• question_answer15)
  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
  View Solution play_arrow

• question_answer16)
  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 clear
  C)
  4 Wb                             done clear
  D)
  2 Wb       done clear
  View Solution play_arrow

• question_answer17)
  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 clear
  C)
     Gauss law            done clear
  D)
  Biot-Savart law    done clear
  View Solution play_arrow

• question_answer18)
  Induced emf in the coil depend upon:
  A)
  conductivity of coil     done clear
  B)
  amount flux done clear
  C)
  rate of change of linked flux done clear
  D)
  resistance coil                                          done clear
  View Solution play_arrow

• question_answer19)
  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
  View Solution play_arrow

• question_answer20)
  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
  View Solution play_arrow

• question_answer21)
  A conducting coil is held stationary in a non-uniform magnetic field. The emf induced in the coil is:
  A)
  maximum                      done clear
  B)
  minimum done clear
  C)
  zero                   done clear
  D)
  Blv done clear
  View Solution play_arrow

• question_answer22)
  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
  View Solution play_arrow

• question_answer23)
  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 clear
  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
  View Solution play_arrow

• question_answer24)
  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
  View Solution play_arrow

• question_answer25)
  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
  View Solution play_arrow

• question_answer26)
  Unit of induced emf is: 
  A)
  ampere                          done clear
  B)
  volt      done clear
  C)
  joule                              done clear
  D)
  electron volt done clear
  View Solution play_arrow

• question_answer27)
     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
  View Solution play_arrow

• question_answer28)
  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
  View Solution play_arrow

• question_answer29)
  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
  View Solution play_arrow

• question_answer30)
  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
  View Solution play_arrow

• question_answer31)
  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 clear
  B)
  \[\frac{\pi }{2}\] done clear
  C)
  \[\frac{-\pi }{6}\]                                    done clear
  D)
  \[\pi \] done clear
  View Solution play_arrow

• question_answer32)
  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_answer33)
  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
  View Solution play_arrow

• question_answer34)
  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
  View Solution play_arrow

• question_answer35)
                   Lenz’s law is consequence of the law of conservation of:
  A)
  momentum                    done clear
  B)
  mass done clear
  C)
  charge               done clear
  D)
  energy done clear
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• question_answer36)
  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
  View Solution play_arrow

• question_answer37)
  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 clear
  C)
  in anticlockwise direction done clear
  D)
  first anticlockwise then clockwise done clear
  View Solution play_arrow

• question_answer38)
  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 clear
  D)
  direction of alternating current done clear
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• question_answer39)
  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_answer40)
  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
  View Solution play_arrow

• question_answer41)
  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)
           done clear
  B)
  done clear
  C)
         done clear
  D)
  done clear
  View Solution play_arrow

• question_answer42)
  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_answer43)
                                    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_answer44)
  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_answer45)
  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_answer46)
  Match the Column I with Column II and mark the correct option from the codes given below:

  	Column I (Planar loops of different  shapes)		Column II (Direction of induced current)
  (A)		(p)	b a c b
  (B)		(q)	c d a b c
  (C)		(r)	b c d a b

  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
  View Solution play_arrow

• question_answer47)
  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
  View Solution play_arrow

• question_answer48)
  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
  View Solution play_arrow

• question_answer49)
  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
  View Solution play_arrow

• question_answer50)
  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
  View Solution play_arrow

• question_answer51)
  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
  View Solution play_arrow

• question_answer52)
  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
  View Solution play_arrow

• question_answer53)
  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
  View Solution play_arrow

• question_answer54)
  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
  View Solution play_arrow

• question_answer55)
  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
  View Solution play_arrow

• question_answer56)
  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
  View Solution play_arrow

• question_answer57)
  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
  View Solution play_arrow

• question_answer58)
  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
  View Solution play_arrow

• question_answer59)
  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
  View Solution play_arrow

• question_answer60)
  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
  View Solution play_arrow

• question_answer61)
  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
  View Solution play_arrow

• question_answer62)
  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
  View Solution play_arrow

• question_answer63)
  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
  View Solution play_arrow

• question_answer64)
  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
  View Solution play_arrow

• question_answer65)
  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
  View Solution play_arrow

• question_answer66)
  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
  View Solution play_arrow

• question_answer67)
  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
  View Solution play_arrow

• question_answer68)
  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
  View Solution play_arrow

• question_answer69)
  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
  View Solution play_arrow

• question_answer70)
  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
  View Solution play_arrow

• question_answer71)
  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
  View Solution play_arrow

• question_answer72)
  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
  View Solution play_arrow

• question_answer73)
  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
  View Solution play_arrow

• question_answer74)
  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
  View Solution play_arrow

• question_answer75)
  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
  View Solution play_arrow

• question_answer76)
  Eddy currents do not cause:
  A)
  heating                          done clear
  B)
  loss of energy done clear
  C)
  sparking                         done clear
  D)
  damping done clear
  View Solution play_arrow

• question_answer77)
  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
  View Solution play_arrow

• question_answer78)
  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_answer79)
  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
  View Solution play_arrow

• question_answer80)
  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_answer81)
  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_answer82)
  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
  View Solution play_arrow

• question_answer83)
  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_answer84)
  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_answer85)
  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_answer86)
  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_answer87)
  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_answer88)
  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
  View Solution play_arrow

• question_answer89)
  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_answer90)
  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_answer91)
  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
  View Solution play_arrow

• question_answer92)
  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_answer93)
  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_answer94)
  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_answer95)
  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_answer96)
  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_answer97)
  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_answer98)
  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_answer99)
  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_answer100)
  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_answer101)
  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_answer102)
  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_answer103)
  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_answer104)
  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_answer105)
                                  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_answer106)
  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_answer107)
  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_answer108)
  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_answer109)
  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_answer110)
  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_answer111)
  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_answer112)
  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_answer113)
  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
  View Solution play_arrow

• question_answer114)
  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_answer115)
  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