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CUET · PHYSICS · PYQ PAPER 2023

A charge of \( 5 \mu C \) moves with a speed of \( 2 \times 10^6 \text{ m/s} \) along the positive \( y \)-axis. A magnetic field \( \vec{B} \) of strength \( (2\hat{i} + \hat{k})\text{T} \) exists in space. The magnetic force acting on the charge is :

  1. A \( (-20\hat{k} + 10\hat{i}) \text{ N} \)
  2. B \( (20\hat{k} - 10\hat{i}) \text{ N} \)
  3. C \( (20\hat{k} + 10\hat{i}) \text{ N} \)
  4. D \( (10\hat{i} + 5\hat{k}) \text{ N} \)
Verified Solution

Answer & Solution

Correct Answer

(B) \( (20\hat{k} - 10\hat{i}) \text{ N} \)

Step-by-step Solution

Detailed explanation

\(v \times B=\left(2 \times 10^6 \hat{j}\right) \times(2 \hat{i}+\hat{k})\) \(v \times B=4 \times 10^6(\hat{j} \times \hat{i})+2 \times 10^6(\hat{j} \times \hat{k})\) Using unit vector rules \((\hat{j} \times \hat{i}=-\hat{k}\) and \(\hat{j} \times \hat{k}=\hat{i})\) :…
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