Which of the following statements are correct?
(A) Electric monopoles do not exist whereas magnetic monopoles exist.
(B) Magnetic field lines due to a solenoid at its ends and outside cannot be completely straight and confined.
(C) Magnetic field lines are completely confined within a toroid.
(D) Magnetic field lines inside a bar magnet are not parallel.
(E) χ = —1 is the condition for a perfect diamagnetic material, where χ is its magnetic susceptibility.
Choose the correct answer from the options given below :
Which of the following statements are correct?
(A) Electric monopoles do not exist whereas magnetic monopoles exist.
(B) Magnetic field lines due to a solenoid at its ends and outside cannot be completely straight and confined.
(C) Magnetic field lines are completely confined within a toroid.
(D) Magnetic field lines inside a bar magnet are not parallel.
(E) χ = —1 is the condition for a perfect diamagnetic material, where χ is its magnetic susceptibility.
Choose the correct answer from the options given below :
The correct option is C (C) and (E) only
The explanation for the correct answer :
The explanation for point C :
Magnetic field lines can be completely contained within the core of a toroid, but they cannot be contained within the core of a straight solenoid. Because no two magnetic field lines may intersect and originate and finish at the same spot (as in a ring), they are restricted to the toroid's core.
For a perfectly diamagnetic substance
The explanation for the incorrect answer :
The explanation for point A :
Magnetic monopoles do not exist because magnetic field lines must form closed loops, starting at one pole and ending at the opposite. The magnetic field lines will not terminate if a monopole escape, which is impossible. As a result, there are no magnetic field lines.
The explanation for point B :
A straight solenoid's magnetic field lines cannot be completely contained between its two ends. Because the flux through the cross-section at each end must be zero, this is the case. The flux through the cross-section at either end would be non-zero if the lines were totally restricted between two ends of a straight solenoid.
The explanation for point D :
As we know magnetic field lines never intersect each other because if they do then there will be two directions of magnetic field lines if we draw a tangent at the point of intersection which is absurd.
So the magnetic field lines outside the bar magnet are circular while inside the magnet is parallel.
Therefore the correct option is C.
(C) and (E) only
The explanation for the correct answer :
The explanation for point C :
Magnetic field lines can be completely contained within the core of a toroid, but they cannot be contained within the core of a straight solenoid. Because no two magnetic field lines may intersect and originate and finish at the same spot (as in a ring), they are restricted to the toroid's core.
For a perfectly diamagnetic substance
The explanation for the incorrect answer :
The explanation for point A :
Magnetic monopoles do not exist because magnetic field lines must form closed loops, starting at one pole and ending at the opposite. The magnetic field lines will not terminate if a monopole escape, which is impossible. As a result, there are no magnetic field lines.
The explanation for point B :
A straight solenoid's magnetic field lines cannot be completely contained between its two ends. Because the flux through the cross-section at each end must be zero, this is the case. The flux through the cross-section at either end would be non-zero if the lines were totally restricted between two ends of a straight solenoid.
The explanation for point D :
As we know magnetic field lines never intersect each other because if they do then there will be two directions of magnetic field lines if we draw a tangent at the point of intersection which is absurd.
So the magnetic field lines outside the bar magnet are circular while inside the magnet is parallel.
Therefore the correct option is C.
