Physics JEE Main Physics: Authentic Shift PYQs (2021-2026) with 2.5-Min Shortcut Tricks & Trap Defense

Correct Answer: a

Explanation: [MLT$^{–2}$ A$^{–2}$] ⇒ [μ] = [MLT$^{–2}$ A$^{–2}$]

Correct Answer: b

Explanation: $\frac{2}{3} s$ The time period of oscillations of magnet $T = 2 \pi \sqrt{\left(\frac{I}{MH}\right)}$                    …..(i) where l = moment of inertia of magnet $= \frac{mL^{2}}{12}$ (_m_ is being the mass of magnet) _M_ = pole strength × _L_ when the three equal parts of magnet are placed on one another with their like poles together, then $l ' = \frac{1}{12} \left(\frac{m}{3}\right) \left(\frac{L}{3}\right)^{2} \times 3$ $= \frac{1}{12} \frac{mL^{2}}{9}$ $= \frac{l}{9}$ and $M ' =$ pole strength $\times \frac{L}{3} \times 3$= M$ Hence, $T ' = 2 \pi \sqrt{\left(\frac{l / 9}{MH}\right)}$ $T ' = \frac{1}{3} \times T$ $T = 2 / 3 \textrm{ } sec$

Correct Answer: 1

Explanation: Detailed pedagogical breakdown based on official NCERT syllabus criteria.

Correct Answer: c

Explanation: I > IV > II > III _U_ = –_MB_ cosθ I > IV > II > III

Correct Answer: a

Explanation: Size of domain will change and orientation also change. ​When soft iron is placed in external uniform magnetic field, torque will act on dipoles in domain. Hence size of domain will change and orientation also change.​