Moving Charges and Magnetism - Result Question 68
69. When a charged particle moving with velocity $\vec{v}$ is subjected to a magnetic field of induction $\vec{B}$, the force on it is non-zero. This implies that
[2006]
(a) angle between $\vec{v}$ and $\vec{B}$ can have any value other than $90^{\circ}$
(b) angle between $\vec{v}$ and $\vec{B}$ can have any value other than zero and $180^{\circ}$
(c) angle between $\vec{v}$ and $\vec{B}$ is either zero or $180^{\circ}$
(d) angle between $\vec{v}$ and $\vec{B}$ is necessarily $90^{\circ}$
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Answer:
Correct Answer: 69. (b)
Solution:
- (b) Force on a particle moving with velocity $v$ in a magnetic field $B$ is $F=q(\vec{v} \times \vec{B})$ If angle between $\vec{v} & \vec{B}$ is either zero or $180^{\circ}$, then value of $F$ will be zero as cross product of $\vec{v}$ and $\vec{B}$ will be zero.
So option (b) is correct.
