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#	Question	Answer
1	Do magnetic field lines intersect?	No.
2	Do like poles of magnets attract or repel?	Repel.
3	What is the equatorial magnetic field of a short bar magnet?	\( B_E = -\frac{\mu_0}{4\pi} \frac{m}{r^3} \).
4	Does a magnetic dipole experience a net force in a uniform magnetic field?	No. It experiences only a torque.
5	Do magnetic field lines form closed loops?	Yes.
6	Can magnetic field lines cross each other?	No.
7	What is relative magnetic permeability?	\( \mu_r = 1 + \chi \).
8	A solenoid has a core with relative permeability 400 and 1000 turns per metre carrying 2 A. What is the magnetic field inside?	1.0 T.
9	What is a magnetic domain?	A region in a ferromagnetic material where atomic magnetic moments are aligned in the same direction.
10	Give an example of a ferromagnetic material.	Iron, cobalt, or nickel.
11	A closely wound solenoid of 2000 turns and area \( 1.6 \times 10^{-4} \) m² carries 4.0 A. What is its magnetic moment?	1.28 A m².
12	What is the SI unit of magnetic flux?	Weber (Wb).
13	Given two identical-looking iron bars, only one of which is magnetised, how can you tell which one is the magnet using only the two bars?	A bar magnet's field is strongest at its two ends (poles) and weakest at its centre. Touch one end of bar A to the middle, then to an end, of bar B: if A feels no force at B's middle but does at B's end, B is the magnet (and vice versa). A mutual repulsion in any trial confirms both are magnetised.
14	In terms of the field \( B_0 = \mu_0 nI \) from the solenoid's current alone and the material's own contribution \( B_m \), what is the total field B inside a solenoid with a magnetic core?	\( B = B_0 + B_m \), where \( B_m = \mu_0 M \) is the extra field contributed by the core's magnetisation M.
15	What is the magnetising current \( I_M \) for that solenoid — the extra current that, without the core, would reproduce the same B?	\( I_M \approx 794 \) A — found from \( B = \mu_0 n(I + I_M) \).
16	Why do paramagnetic materials show no net magnetisation in the absence of an external field, despite their atoms having permanent dipole moments?	Ceaseless random thermal motion randomises the orientation of the individual atomic dipole moments, so they average to zero.
17	Roughly how large is the relative magnetic permeability of a ferromagnetic material?	Greater than 1000.
18	Besides diamagnetic, paramagnetic, and ferromagnetic, what other (more exotic) categories of magnetic material exist?	Ferrimagnetic, anti-ferromagnetic, and spin-glass materials, among others.
19	Two bar magnets, each of magnetic moment m, are arranged with their axes meeting at an angle θ between them. Comparing θ = 180° (antiparallel), 90°, 60°, and 30°, which arrangement gives the highest net magnetic dipole moment? (NEET 2014)	θ = 30° — combining two equal moments at angle θ by the parallelogram law gives a resultant \( m_{net}=\sqrt{2m^2(1+\cos\theta)} \), which grows as θ shrinks. It is zero at 180° (antiparallel) and largest at the smallest angle offered, 30°.
20	Where does the word 'magnet' come from?	From Magnesia, the name of an island in Greece where magnetic ore deposits were found, as early as 600 BC.
21	What is the SI unit of magnetic field B?	Tesla (T).
22	What theory explains the connection between perfect diamagnetism and perfect conductivity in a superconductor, and who proposed it?	The BCS theory, proposed by Bardeen, Cooper, and Schrieffer in 1957 — eventually recognised with a Nobel Prize in Physics in 1970.
23	A charged particle of charge q moves in a circle of radius R with uniform speed v. What orbital magnetic moment is associated with this motion? (AIPMT 2007)	\( m=\dfrac{qvR}{2} \) — the circulating charge is equivalent to a current loop (current \(I=\frac{qv}{2\pi R}\), area \(\pi R^2\)), the same picture used to explain orbiting atomic electrons in diamagnetism.