Moving Charges and Magnetism - Result Question 69
70. A very long straight wire carries a current I. At the instant when a charge $+Q$ at point $P$ has velocity $\vec{v}$, as shown, the force on the charge is
[2005]
(a) along $O Y$
(b) opposite to $O Y$
(c) along $O X$
(d) opposite to $O X$
Show Answer
Answer:
Correct Answer: 70. (a)
Solution:
- (a) The direction of $\vec{B}$ is along $(-\hat{k})$
$\therefore$ The magnetic force
$\vec{F}=Q(\vec{v} \times \vec{B})=Q(v \hat{i}) \times B(-\hat{k})=Q v B \hat{j}$
$\Rightarrow \vec{F}$ is along $O Y$.
