12th Class Physics Magnetism Question Bank

done Case Based (MCQs) - Magnetism and Matter Total Questions - 40

• question_answer1)

  Direction: Q.1 to Q.5

  Current loop behaves like a magnetic dipole and has a magnetic field. They behave just like a magnet. Interesting part is, it depends upon the direction of current in loop which decides whether magnetic field line is in outward or inward direction. With the help of this outward and inward direction of magnetic field, north and south poles get decided.

  Anticlockwise direction of current creates north pole (outward direction magnetic field) and clockwise direction of current creates a south pole (inward direction magnetic field). Magnetic dipole moment \[\overrightarrow{\text{M}}\] with the circular current loop carrying a current I and of area A. The magnitude of m is given by

  \[|\overrightarrow{M}|=I\times A\]

  Current in the circular coil produces magnetic field and Amperes found out that magnetic field created due to circular coil is similar to the magnetic field due to a bar magnet. Wood screw head sign shows that direction of screw is inward because we are not able to see pointed part of screw and so direction is inward. This inward direction of screw denotes the direction of the magnetic field.

  Read the given passage carefully and give answer of the following questions:

  A thin circular wire carrying a current l, has a magnetic moment M. The shape of the wire is changed to a square and it carries the same current. It will have a magnetic moment:
  A)
  \[\frac{4}{{{\pi }^{2}}}M\]                done clear
  B)
  M done clear
  C)
              \[\frac{4}{\pi }M\]          done clear
  D)
              \[\frac{\pi }{4}M\] done clear
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• question_answer2)
  A current carrying loop is placed in a uniform magnetic field in four different orientations as shown in figure. Arrange them in the decreasing order of potential energy.                                              
  A)
  IV, III, II, I                     done clear
  B)
  I, IV, II, III done clear
  C)
  IV, II, III, I                     done clear
  D)
  I, II, III, IV done clear
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• question_answer3)
                                        Point out the correct direction of magnetic field in the given figures:
  A)
          done clear
  B)
  done clear
  C)
  done clear
  D)
                done clear
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• question_answer4)
  Two identical bar magnets are fixed with their centres at a distance d apart. A stationary charge Q is placed at P in between the gap of the two magnets at a distance D from the centre O as shown in the figures. The force on the charge Q is:
  A)
  zero done clear
  B)
  directed along OP done clear
  C)
  directed along PO done clear
  D)
  directed perpendicular to the plane of paper done clear
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• question_answer5)
  In a bar magnet, magnetic lines of force:
  A)
  are produced only at north pole like rays of light from a bulb. done clear
  B)
  starts from north pole and ends at the south pole. done clear
  C)
  emerge in circular paths from the middle of the bar. done clear
  D)
  run continuously through the bar and outside. done clear
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• question_answer6)

  Direction: Q.6 to Q.10

  The field of a hollow wire with constant current is homogenous. Curves in the graph shown give, as functions of radius distance r, the magnitude B of the magnetic field inside and outside four long wires a, b, c and d carrying currents that are uniformly distributed across the cross-sections of the wires. Overlapping portions of the plots are indicated by double labels.

  Read the given passage carefully and give answer of the following questions:

  Which wire has the greatest magnitude of the magnetic field on the surface?
  A)
  a                       done clear
  B)
  b          done clear
  C)
  c                       done clear
  D)
  d done clear
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• question_answer7)
  The current density in a wire a is:
  A)
  greater than in wire c done clear
  B)
  less than in wire c done clear
  C)
  equal to that in wire c done clear
  D)
  not comparable to that of in wire c due to lack of information done clear
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• question_answer8)
  Which wire has the greatest radius?
  A)
  a          done clear
  B)
  b           done clear
  C)
  c          done clear
  D)
  d           done clear
  View Solution play_arrow

• question_answer9)
                  A direct current l flows along the length of an infinitely long straight thin walled pipe, then the magnetic field is:
  A)
  uniform throughout the pipe but not zero.              done clear
  B)
  zero only along the axis of the pipe. done clear
  C)
  zero at any point inside the pipe.   done clear
  D)
  maximum at the centre and minimum at the edges. done clear
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• question_answer10)
           In a coaxial, straight cable, the central conductor and the outer conductor carry equal currents in opposite direction. The magnetic field is zero:
  A)
  outside the cable. done clear
  B)
  inside the inner conductor. done clear
  C)
  inside the outer conductor. done clear
  D)
  in between the two conductor. done clear
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• question_answer11)

  Direction: Q.11 to Q.15

  By analogy to Gauss's law of electrostatics, we can write Gauss's law of magnetism as \[\oint{\overrightarrow{B}\cdot \overrightarrow{d\,S}={{\mu }_{0}}{{m}_{inside}}}\] where \[\oint{\overrightarrow{B}\cdot \overrightarrow{d\,S}}\] is the magnetic flux and \[{{m}_{inside}}\] is the net pole strength inside the closed surface.

  We do not have an isolated magnetic pole in nature. At least one has been found to exist till date. The smallest unit of the source of magnetic field is a magnetic dipole where the net magnetic pole is zero. Hence, the net magnetic pole enclosed by any closed surface is always zero.

  Correspondingly, the flux of the magnetic field through any closed surface is zero.

  Read the given passage carefully and give answer of the following questions:

  Consider the two idealised systems

  (i) A parallel plate capacitor with large plates and small separation and

  (ii) a long solenoid of length L>>R, radius of cross-section.

  In (i) \[\overrightarrow{E}\] is ideally treated as a constant between plates and zero outside. In (ii) magnetic field is constant inside the solenoid and zero outside. These idealised assumptions, however, contradict fundamental laws as below:

  A)
  case (i) contradicts Gauss's law for electrostatic fields. done clear
  B)
  case (ii) contradicts Gauss's law for magnetic fields.     done clear
  C)
  case (i) agrees with \[\oint{\overrightarrow{E}\cdot \overrightarrow{dl}=0}\]. done clear
  D)
  case (ii) contradicts \[\oint{\overrightarrow{E}\cdot \overrightarrow{dl}={{l}_{en}}}\]. done clear
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• question_answer12)
  The net magnetic flux through any closed surface, kept in a magnetic field is:
  A)
  zero                               done clear
  B)
  \[\frac{{{\mu }_{0}}}{4\pi }\] done clear
  C)
              \[4\pi {{\mu }_{0}}\]     done clear
  D)
              \[\frac{4{{\mu }_{0}}}{\pi }\] done clear
  View Solution play_arrow

• question_answer13)
  A closed surface S encloses a magnetic dipole of magnetic moment 2ml. The magnetic flux emerging from the surface is:
  A)
      \[{{\mu }_{0}}m\]                     done clear
  B)
  zero done clear
  C)
              \[2{{\mu }_{0}}m\]       done clear
  D)
              \[\frac{2m}{{{\mu }_{0}}}\] done clear
  View Solution play_arrow

• question_answer14)
  Which of the following is not a consequence of Gauss's law?
  A)
  The magnetic poles always exist as unlike pairs of equal strength. done clear
  B)
  If several magnetic lines of force enter in a closed surface, then an equal number of lines of force must leave that surface. done clear
  C)
  There are abundant sources or sinks of the magnetic field inside a closed surface. done clear
  D)
  Isolated magnetic poles do not exist. done clear
  View Solution play_arrow

• question_answer15)
  The surface integral of a magnetic field over a surface:
  A)
  is proportional to mass enclosed. done clear
  B)
  is proportional to charge enclosed. done clear
  C)
  is zero. done clear
  D)
  equal to its magnetic flux through that surface. done clear
  View Solution play_arrow

• question_answer16)

  Direction: Q.16 to Q.20

  The Earth's magnetic field extends millions of kilometres into outer space and looks very much like a bar magnet. The Earth's south magnetic pole is actually near the north-pole and the north magnetic pole is in Antarctica. This is why a compass magnet's north-pole actually points north (north and south poles attract). The Earth's magnetic field extends far and wide but is very weak in terms of field strength.

  Magnetic Declination: It is defined as the angle between the true north and the magnetic north. On the horizontal plane, the true north is never at a constant position and keeps varying depending upon the position on the Earth's surface and time.

  Magnetic Inclination: The magnetic inclination is also known as the angle of dip. It is the angle made the plane on the Earth's surface. At the magnetic equator, the angle of dip is \[0{}^\circ \] and at the magnetic poles, the angle of dip is \[90{}^\circ .\]

  Horizontal Component of the Earth’s Magnetic Field:

  There are two components to explain the intensity of the Earth's magnetic field: Horizontal component \[({{B}_{H}})\] and vertical component \[({{B}_{V}})\].

  \[\tan \delta ={{B}_{V}}/{{B}_{H}}\]

  Read the above passage carefully and give the answer of the following questions:

    The vertical component of the Earth's magnetic field is at a place is \[\sqrt{3}\] times the horizontal component. What is the value of angle of dip at this place?
  A)
  \[60{}^\circ \]                           done clear
  B)
  \[45{}^\circ \]       done clear
  C)
  \[90{}^\circ \]                           done clear
  D)
  \[30{}^\circ \]         done clear
  View Solution play_arrow

• question_answer17)
  A bar magnet is placed with its north pole pointing Earth's north. The points of zero magnetic field will be in which direction from the centre of the magnet?
  A)
  North and south done clear
  B)
  East and west done clear
  C)
  North-east and south-west done clear
  D)
  North-west and south-east done clear
  View Solution play_arrow

• question_answer18)
  Which of the following statements is true about magnetic lines of force?
  A)
  Magnetic lines of force are always closed.               done clear
  B)
  Magnetic lines of force always intersect Earth other. done clear
  C)
  Magnetic lines of force tend to crowd far away from the poles of the magnet. done clear
  D)
  Magnetic lines of force do not pass through the vacuum. done clear
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• question_answer19)
  A long magnet is cut into two parts such that the ratio of their lengths is 2 :1. What is the ratio poles strength of both the section?
  A)
  1 : 2                              done clear
  B)
  2 : 1       done clear
  C)
  4 : 1                              done clear
  D)
  Equal   done clear
  View Solution play_arrow

• question_answer20)
  If a man in Antarctica, then the angle of dip for the man is:
  A)
  \[60{}^\circ \]                           done clear
  B)
  \[45{}^\circ \]       done clear
  C)
  \[90{}^\circ \]                           done clear
  D)
  \[30{}^\circ \] done clear
  View Solution play_arrow

• question_answer21)

  Direction: Q.21 to Q.25

  Earth's magnetic field is dynamo effect. The circulating electric current in the Earth's core is the origin of the magnetic field. The fluid motion in Earth's outer core moves liquid iron and generates an electric current. The rotation of Earth on its axis causes these electric current to form a magnetic field which extends around a planet. The magnetic field magnitude measured at the surface of the Earth is about a half Gauss.

  The magnetic field is extremely important to sustaining life on Earth. Without it, we would be exposed to high amounts of radiation from the Sun and our atmosphere would be free to leak into space. This is likely what happened to the atmosphere on Mars. As Mars doesn't have flowing liquid metal in its core, it doesn't produce the same dynamo effect. This left the plant with a very weak magnetic field, allowing for its atmosphere to be stripped away by solar winds, leaving it uninhabitable. Based upon the study of lava flows throughout the world, it has been proposed that the Earth's magnetic field reverses at an average interval of approximately 3,00,000 years. However, the last' such event, occurred some 7,80,000 years ago.

  Read the above passage carefully and give the answer of the following questions:

  Which of the following is responsible for Earth's magnetic field?
  A)
  Circulating electric current in Earth's core done clear
  B)
  Rotation of Earth done clear
  C)
  Attraction due to other celestial bodies done clear
  D)
  Solar flares done clear
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• question_answer22)
  Electric current in the Earth's core is generated due to:
  A)
  Movement of charged particle in the atmosphere. done clear
  B)
  Flowing of liquid metal in the outer core. done clear
  C)
  Electric discharges during thunderstorm. done clear
  D)
  Its revolution around the Sun. done clear
  View Solution play_arrow

• question_answer23)
  Which planet has no own magnetic field?
  A)
  Jupiter                           done clear
  B)
  Neptune done clear
  C)
  Mars                             done clear
  D)
  Mercury done clear
  View Solution play_arrow

• question_answer24)
  Magnetic field strength at the Earth's surface is:
  A)
  5 Gauss                         done clear
  B)
  0.5 Gauss done clear
  C)
  500 Gauss                     done clear
  D)
  Cannot be measured done clear
  View Solution play_arrow

• question_answer25)
  Which of the following statement is true?
  A)
  Earth's magnetic field is due to electric current induced in the ionosphere.    done clear
  B)
  The average magnetic field strength in the Earth's outer core is equal to the magnetic field at the surface done clear
  C)
  Earth's magnetic field reverses at an average interval of approximately 3,00,000 years. done clear
  D)
  Angle of dip is same at every point of the surface of Earth. done clear
  View Solution play_arrow

• question_answer26)
     

  Direction: Q.26 to Q.30

  The Earth's magnetic field at a point on its surface is usually characterised by three quantities: (a) declination (b) inclination or dip and (c) horizontal component of the field. These are known as the elements of the Earth's magnetic field. At a place, angle between geographic meridian and magnetic meridian is defined as magnetic declination, whereas angle made by the Earth's magnetic field with the horizontal in magnetic meridian is known as magnetic dip.

  Read the above passage carefully and give the answer of the following questions:

                              In a certain place, the horizontal component of magnetic field is \[\frac{1}{\sqrt{3}}\] times the vertical component. The angle of dip at this place is:                                             
  A)
  zero                               done clear
  B)
  \[\pi /3\]        done clear
  C)
  \[\pi /2\]                         done clear
  D)
  \[\pi /6\] done clear
  View Solution play_arrow

• question_answer27)
  The angle between the true geographic north and the north shown by a compass needle is called as:
  A)
  inclination                      done clear
  B)
  magnetic declination done clear
  C)
  angle of meridian       done clear
  D)
    magnetic pole done clear
  View Solution play_arrow

• question_answer28)
                      The angles of dip at the poles and the equator respectively are:
  A)
  \[30{}^\circ ,\text{ }60{}^\circ \]                      done clear
  B)
  \[0{}^\circ ,\text{ }90{}^\circ \]     done clear
  C)
  \[45{}^\circ ,\text{ }90{}^\circ \]                      done clear
  D)
  \[90{}^\circ ,\text{ }0{}^\circ \] done clear
  View Solution play_arrow

• question_answer29)
  A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It:
  A)
  will become rigid showing no movement. done clear
  B)
  will stay in any position. done clear
  C)
  will stay in north-south direction only. done clear
  D)
  will stay in east-west direction only. done clear
  View Solution play_arrow

• question_answer30)
  Select the correct statement from the following:
  A)
  The magnetic dip is zero at the centre of the Earth. done clear
  B)
  Magnetic dip decreases as we move away from the equator towards the magnetic pole. done clear
  C)
  Magnetic dip increases as we move away from the equator towards the magnetic pole. done clear
  D)
  Magnetic dip does not vary from place to place. done clear
  View Solution play_arrow

• question_answer31)

  Direction: Q.31 to Q.35

  The magnetic field lines of the Earth resemble that of a hypothetical magnetic dipole located at the centre of the Earth. The axis of the dipole is presently tilted by approximately \[11.3{}^\circ \] with respect to the axis of rotation of the Earth.

  The pole near the geographic north pole of the Earth is called the north magnetic pole and the pole near the geographic south-pole is called south magnetic pole.

  Read the given passage carefully and give the answer of the following questions:

                                  The strength of the Earth's magnetic field varies from place to place on the Earth's surface, its value being of the order of:
  A)
              \[{{10}^{5}}T\]                      done clear
  B)
  \[{{10}^{6}}T\] done clear
  C)
              \[{{10}^{-5}}T\]          done clear
  D)
              \[{{10}^{8}}T\] done clear
  View Solution play_arrow

• question_answer32)
  A bar magnet is placed North-South with its North-pole due North. The points of zero magnetic field will be in which direction from centre of magnet?
  A)
  North-South done clear
  B)
  East-West done clear
  C)
  North-East and South-West done clear
  D)
  None of the above done clear
  View Solution play_arrow

• question_answer33)
  The value of angle of dip is zero at the magnetic equator because on it:
  A)
  \[{{B}_{V}}\] and \[{{B}_{H}}\] are equal done clear
  B)
  the values of \[{{B}_{V}}\] and  \[{{B}_{H}}\] are zero. done clear
  C)
  the value of \[{{B}_{V}}\] is zero. done clear
  D)
  the value of \[{{B}_{H}}\] is zero.               done clear
  View Solution play_arrow

• question_answer34)
  The angle of dip at a certain place, where the horizontal and vertical components of the Earth's magnetic field are equal, is:
  A)
  \[30{}^\circ \]                           done clear
  B)
  \[90{}^\circ \]       done clear
  C)
  \[60{}^\circ \]                           done clear
  D)
  \[45{}^\circ \] done clear
  View Solution play_arrow

• question_answer35)
  At a place, angle of dip is \[30{}^\circ \]. If horizontal component of Earth's magnetic field is \[{{B}_{H}}\], then the total intensity of magnetic field will be:
  A)
              \[\frac{{{B}_{H}}}{2}\]                                  done clear
  B)
  \[\frac{2{{B}_{H}}}{\sqrt{3}}\] done clear
  C)
              \[{{B}_{H}}\sqrt{\frac{3}{2}}\] done clear
  D)
              \[2{{B}_{H}}\] done clear
  View Solution play_arrow

• question_answer36)

  Direction: Q.35 to Q.40

  When the atomic dipoles are aligned partially or fully, there is a net magnetic moment in the direction of the field in any small volume of the material. The actual magnetic field inside material placed in magnetic field is the sum of the applied magnetic field and the magnetic field due to magnetisation. This field is called magnetic intensity (H).

  \[H=\frac{B}{{{\mu }_{0}}}-M\]

  where M is the magnetisation of the material, \[{{\mu }_{0}}\] is the permittivity of vacuum and B is the total magnetic field. The measure that tells us how a magnetic material responds to an external field is given by a dimensionless quantity is appropriately called the magnetic susceptibility: for a certain class of magnetic materials, intensity of magnetisation is directly proportional to the magnetic intensity.

  Read the given passage carefully and give the answer of the following questions:

  Magnetisation of a sample is:
  A)
  volume of sample per unit magnetic moment. done clear
  B)
  net magnetic moment per unit volume. done clear
  C)
  ratio of magnetic moment and pole strength. done clear
  D)
  ratio of pole strength to magnetic moment. done clear
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• question_answer37)
  Identify the wrongly matched quantity and unit pair.
  A)

  Pole strength

  (i)

  -Am

  done clear
  B)

  Magnetic susceptibility

  (ii)

  -dimensionless number

  done clear
  C)

  Intensity of magnetization

  (iii)

  \[-A{{m}^{-1}}\]

  done clear
  D)

  Magnetic permeability

  (iv)

  -Henry m

  done clear
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• question_answer38)
  A bar magnet has length 3 cm, cross-sectional area \[2\text{ }c{{m}^{2}}\] and magnetic moment \[3\text{ }A{{m}^{2}}\]. The intensity of magnetisation of bar magnet is:
  A)
  \[2\times {{10}^{5}}A/m\] done clear
  B)
  \[3\times {{10}^{5}}A/m\] done clear
  C)
  \[4\times {{10}^{5}}A/m\]                    done clear
  D)
  \[5\times {{10}^{5}}A/m\] done clear
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• question_answer39)
  A solenoid has core of a material with relative permeability 500 and its windings carry a current of 1 A. The number of turns of the solenoid is 500 per metre. The magnetization of the material is nearly:
  A)
  \[2.5\times {{10}^{3}}A{{m}^{-1}}\]              done clear
  B)
  \[2.5\times {{10}^{5}}A{{m}^{-3}}\] done clear
  C)
  \[2.0\times {{10}^{3}}A{{m}^{-1}}\]           done clear
  D)
  \[2.0\times {{10}^{5}}A{{m}^{-1}}\] done clear
  View Solution play_arrow

• question_answer40)
  The relative permeability of iron is 6000. Its magnetic susceptibility is:
  A)
  5999                             done clear
  B)
  6001 done clear
  C)
  \[6000\times {{10}^{-7}}\]                    done clear
  D)
  \[6000\times {{10}^{7}}\] done clear
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