12th Class Physics Magnetism Question Bank

done MCQs - Moving Charges and Magnetism Total Questions - 21

• question_answer1)
  Two charged particles traverse identical helical paths in a completely opposite sense in a uniform magnetic field \[B={{B}_{0}}k\].
  A)
  They have equal z-components of momenta. done clear
  B)
  They must have equal charges. done clear
  C)
  They necessarily represent a particle- antiparticle pair. done clear
  D)
  The   charge   to   mass   ratio   satisfy: \[{{\left( \frac{e}{m} \right)}_{1}}+{{\left( \frac{e}{m} \right)}_{2}}=0\] done clear
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• question_answer2)
  Biot-Savart law indicates that the moving electrons (velocity v) produce a magnetic field B such that
  A)
  \[B\bot v\]                                  done clear
  B)
  \[B||v\]. done clear
  C)
  it obeys inverse cube law. done clear
  D)
  it is along the line joining the electron and point of observation. done clear
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• question_answer3)
  A current carrying circular loop of radius R is placed in the x - y plane with centre at the origin. Half of the loop with x > 0 is now bent so that it now lies in the y - z plane.
  A)
  The magnitude of magnetic moment now diminishes. done clear
  B)
  The magnetic moment does not change. done clear
  C)
  The magnitude of B at (0.0.z), z >>R increases. done clear
  D)
  The magnitude of B at (0.0.z), z >>R is unchanged. done clear
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• question_answer4)
  A circular current loop of magnetic moment M is in an arbitrary orientation in an external magnetic field B. The work done to rotate the loop by \[{{30}^{\operatorname{o}}}\] about an axis perpendicular to its plane is
  A)
  MB done clear
  B)
  \[\frac{\sqrt{3}\operatorname{MB}}{2}\] done clear
  C)
  \[\frac{\operatorname{MB}}{2}\] done clear
  D)
  zero. done clear
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• question_answer5)
  When a charge of 1C moving with velocity 1 m/s normal to a magnetic field experiences a force 1 N, then the magnitude of the magnetic field is
  A)
  1 Gauss done clear
  B)
  1 Tesia done clear
  C)
  1 Orested done clear
  D)
  None of the above done clear
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• question_answer6)
  An electron is projected with uniform velocity along the axis of a current carrying long solenoid. Which of the following is true?
  A)
  The electron will be accelerated along the axis. done clear
  B)
  The electron path will be circular about the axis. done clear
  C)
  The electron will experience a force at \[{{45}^{\operatorname{o}}}\] to the axis and hence execute a helical path. done clear
  D)
  The electron will continue to move with uniform velocity along the axis of the solenoid. done clear
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• question_answer7)
  When a charged particle moves through a magnetic field perpendicular to its direction. Then
  A)
  Linear momentum changes done clear
  B)
  kinetic energy remains constant done clear
  C)
  Both [a] and [b] done clear
  D)
  Both linear momentum and kinetic energy varies done clear
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• question_answer8)
  A length L of wire carries a steady current I. It is bent first to form a circular plane coil of one turn. A current I flowing through it produces a magnetic, field B at the centre of the coil. The same length is now bent more sharply to form a double loop of smaller radius. The magnetic field at the centre caused by the same current is
  A)
  B done clear
  B)
  2B done clear
  C)
  4B done clear
  D)
  B/2 done clear
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• question_answer9)
  A straight conductor carries a current from south to north. Point P and Q lie to the east and west of it at the same distance. The magnetic field at P is
  A)
  equal to magnetic field at Q. done clear
  B)
  smaller than the magnetic field at Q. done clear
  C)
  greater than the magnetic field at Q. done clear
  D)
  cannot be predicted unless the value if I is known. done clear
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• question_answer10)
  Magnetic field due to a straight solenoid at any point inside it is B =\[{{\mu }_{0}}ni\]. Magnetic field at the end of the solenoid is
  A)
  B done clear
  B)
  B/2 done clear
  C)
  2B done clear
  D)
  B/4                   done clear
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• question_answer11)
  At any point, empty space surrounded by a toroid, the magnetic field is \[{{B}_{1}}\]. At any point, outside the toroid, the magnetic field is \[{{\operatorname{B}}_{2}}\].
  A)
  \[{{B}_{1}}\]>\[{{\operatorname{B}}_{2}}\] done clear
  B)
  \[{{\operatorname{B}}_{2}}\]>\[{{B}_{1}}\]               done clear
  C)
  \[{{B}_{1}}\]=\[{{\operatorname{B}}_{2}}\] done clear
  D)
  \[{{B}_{1}}\]=\[{{\operatorname{B}}_{2}}\]=0 done clear
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• question_answer12)

  An infinitely long straight conductor is bent into the shape as shown in the figure. Current in it is i and the radius of the circular loop is r. The magnetic field at its centre is

   
  A)
  Zero done clear
  B)
  Infinite done clear
  C)
  \[\frac{{{\mu }_{0}}i}{2\pi r}(\pi -1)\] done clear
  D)
  \[\frac{{{\mu }_{0}}i}{2\pi r}(\pi +1)\] done clear
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• question_answer13)
  A solenoid of 1.5 metre length and 4.0 cm diameter has 10 turn per cm. A current of 5 A ampere is flowing through it. The magnetic field at axis inside the solenoid is
  A)
  \[2\pi \times ~{{10}^{-3}}\text{ }\operatorname{T}\] done clear
  B)
  \[2\pi \times ~{{10}^{-3}}\text{ G}\] done clear
  C)
  \[2\pi \times ~{{10}^{-7}}\text{ T}\] done clear
  D)
  \[2\pi \times ~{{10}^{-7}}\text{ G}\] done clear
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• question_answer14)
  The strength of the magnetic field at distance r from a long straight current carrying wire is B. The field at a distance r/2 will be
  A)
  B done clear
  B)
  2B done clear
  C)
  B/2 done clear
  D)
  B/4 done clear
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• question_answer15)
  In a moving coil galvanometer, current in the coil is
  A)
  directly proportional to angle of deflection. done clear
  B)
  inversely proportional to the angle of deflection. done clear
  C)
  directly proportional to the square root of the angle of deflection. done clear
  D)
  inversely proportional to the square root of the angle of deflection. done clear
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• question_answer16)
  Current sensitivity of a galvanometer is given by
  A)
  C\[\theta \]/nBA done clear
  B)
  nBA/C done clear
  C)
  nBA/CG done clear
  D)
  CG/nBA done clear
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• question_answer17)
  The deflecting torque acting on the coil of a galvanometer is
  A)
  inversely proportional to number of turns. done clear
  B)
  inversely proportional to current flowing. done clear
  C)
  inversely proportional to area of the coil. done clear
  D)
  directly proportional to the magnetic field strength. done clear
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• question_answer18)
  To convert a galvanometer to ammeter a shunt S is to be connected with the galvanometer. The effective resistance of the ammeter then is
  A)
  GS/(G+S) done clear
  B)
  (G+S)/GS done clear
  C)
  G+S done clear
  D)
  None of the above done clear
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• question_answer19)
  A galvanometer of 100 \[\Omega \] resistance gives full scale deflection for 10 mA current. To use it as an ammeter of 10 A range, the resistance of the shunt required is
  A)
  10 \[\Omega \] done clear
  B)
  0.10 \[\Omega \] done clear
  C)
  0.01 \[\Omega \] done clear
  D)
  0.001 \[\Omega \] done clear
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• question_answer20)
  An ammeter gives full scale deflection when current of 1.0 A is passed in it. It is converted into a 100 A range ammeter. What will be the ratio of the shunt resistance and its resistance?
  A)
  1: 9 done clear
  B)
  9 :1 done clear
  C)
  1:11 done clear
  D)
  11:1 done clear
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• question_answer21)
  A galvanometer can be converted into a voltmeter by connecting a
  A)
  high resistance in series. done clear
  B)
  high resistance in parallel. done clear
  C)
  low resistance in parallel. done clear
  D)
  low resistance in series. done clear
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