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Physics · Moving Charges and Magnetic Field

JEE Main 2025 — 3 April, Evening Shift — Question 56

Given below are two statements: one is labelled as Assertion A\mathbf{A} and the other is labelled as Reason R\mathbf{R}

Assertion A : If Oxygen ion (O−2)\left(\mathrm{O}^{-2}\right) and Hydrogen ion (H+)\left(\mathrm{H}^{+}\right)enter normal to the magnetic field with equal momentum, then the path of O−2\mathrm{O}^{-2} ion has a smaller curvature than that of H+\mathrm{H}^{+}.

Reason R:A proton with same linear momentum as an electron will form a path of smaller radius of curvature on entering a uniform magnetic field perpendicularly.

In the light of the above statements, choose the correct answer from the options given below

  1. Option A:

    A\mathbf{A} is true but R\mathbf{R} is false

    Correct
  2. Option B:

    Both A\mathbf{A} and R\mathbf{R} are true and R\mathbf{R} is the correct explanation of A\mathbf{A}

  3. Option C:

    Both A\mathbf{A} and R\mathbf{R} are true but R\mathbf{R} is NOT the correct explanation of A\mathbf{A}

  4. Option D:

    AA is false but RR is true

Answer: A

Step-by-step solution

R=mvqBR=\frac{m v}{q B} (A) mv,Bm v, B are same for O2−&H+\mathrm{O}^{2-} \& \mathrm{H}^{+}therefore

R∝1∣q∣R \propto \frac{1}{|q|} therefore (A) is correct (B) R=mvqB;mv,q,BR=\frac{m v}{q B} ; m v, q, B

are same both therefore (R) is incorrect

Answer key and solution verified before publishing.

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Exam
JEE Main 2025
Paper
3 April, Evening Shift
Subject
Physics
Chapter
Moving Charges and Magnetic Field
Topic
Motion of Charged Particles in magnetic Fields

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