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 x is its magnetic susceptibility.
Choose the correct answer from the options given below :

Solution

Physics sir · 4 steps

Lock in the two statements you are sure are true, C and E, then pick the only option that has both.

1. Statement A. It is reversed. Electric monopoles exist: an isolated charge such as an electron is one. Magnetic monopoles have never been found, so A is false.
2. Statement C. In an ideal toroid the field lines are closed circles that run entirely inside the core. The field outside is zero, so C is true.
3. Statement E. A perfect diamagnet, such as a superconductor, pushes the field out completely, so B = 0 inside even when H ≠ 0. That forces μᵣ = 1 + χ = 0, so E is true.

   B = μ₀ (1 + χ) H = 0 ⇒ χ = -1

   Option	Has false A?	Has true C?	Has true E?
   (a) A and B	yes	no	no
   (b) B and C	no	yes	no
   (c) C and E	no	yes	yes
   (d) B and D	no	no	no

4. So. Every other option either includes the false statement A or leaves out C or E, which are both true. Statements B and D are not needed to decide. Only (c) contains both C and E without A.

The idea to keep. Perfect diamagnet means B = 0 inside, so μᵣ = 0 and χ = -1. In statement-combination questions, settle the statements you are certain of first and let them eliminate the options.

Answer from the NTA final answer key. Solution by PrepWiser.