JEE Mains · Physics · STD 12 - Moving charges and magnetism
- JEE Mains 2026
- Medium
- Numerical
The charged particle moving in a uniform magnetic field of \((3\hat{i} + 2\hat{j})\) T has an acceleration \(\left(4\hat{i} - \dfrac{x}{2}\hat{j}\right)\) m/s\(^2\). The value of \(x\) is __________.
Pick an option to check your answer.
Answer & Solution
Correct Answer
(A) 12
Step-by-step Solution
Detailed explanation
The magnetic force on a moving charged particle is given by \(\vec{F} = q(\vec{v} \times \vec{B})\).
Since the acceleration \(\vec{a}\) is in the direction of the magnetic force, it must be perpendicular to the magnetic field \(\vec{B}\).
Therefore, the dot product of acceleration and magnetic field is zero:
\(\vec{a} \cdot \vec{B} = 0\)
Substituting the given vectors:
\(\left(4\hat{i} - \dfrac{x}{2}\hat{j}\right) \cdot (3\hat{i} + 2\hat{j}) = 0\)
\((4)(3) + \left(-\dfrac{x}{2}\right)(2) = 0\)
\(12 - x = 0\)
\(x = 12\)
Answer: \(12\)
Since the acceleration \(\vec{a}\) is in the direction of the magnetic force, it must be perpendicular to the magnetic field \(\vec{B}\).
Therefore, the dot product of acceleration and magnetic field is zero:
\(\vec{a} \cdot \vec{B} = 0\)
Substituting the given vectors:
\(\left(4\hat{i} - \dfrac{x}{2}\hat{j}\right) \cdot (3\hat{i} + 2\hat{j}) = 0\)
\((4)(3) + \left(-\dfrac{x}{2}\right)(2) = 0\)
\(12 - x = 0\)
\(x = 12\)
Answer: \(12\)
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