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NEET UG 2021 · Physics · Question 47

NEET 2021 Physics, question 47

Question 47 of the NEET 2021 paper (code O1) is a Physics question from Moving Charges and Magnetism. Its idea, Magnetic Force on a Moving Charge, was asked only this once in NEET 2017–2026. The NTA final answer key gives option 4.

Updated 2026-10-08

Q47 · Physics

In the product

F⃗=q(v⃗×B⃗)\vec{F} = q(\vec{v}\times\vec{B})

=qv⃗×(Bi^+Bj^+B0k^)= q\vec{v}\times(B\hat{i}+B\hat{j}+B_0\hat{k})

For q = 1 and v⃗=2i^+4j^+6k^\vec{v} = 2\hat{i}+4\hat{j}+6\hat{k} and

F⃗=4i^−20j^+12k^\vec{F} = 4\hat{i}-20\hat{j}+12\hat{k}

What will be the complete expression for B⃗\vec{B} ?

  1. 18i^+8j^−6k^8\hat{i}+8\hat{j}-6\hat{k}
  2. 26i^+6j^−8k^6\hat{i}+6\hat{j}-8\hat{k}
  3. 3−8i^−8j^−6k^-8\hat{i}-8\hat{j}-6\hat{k}
  4. 4−6i^−6j^−8k^-6\hat{i}-6\hat{j}-8\hat{k}Official answer

Official answer: option 4 · NTA final answer key

Same idea

The only question on Magnetic Force on a Moving Charge

No other NEET paper from 2017–2026 tested this exact idea.

Magnetic Force on a Moving Charge: every question and how it was framed

The chapter

Moving Charges and Magnetism in ten years of NEET

22 questions from 2017–2026, asked in 10 of 10 papers, about 2.1 a paper. Magnetic Force on Charges and Currents alone had 10.

Chapter analysisStudy this chapterPractise this chapter

Moving Charges and Magnetism: questions per paper

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