A) E and B both are parallel to v
B) E is parallel to v but perpendicular to B
C) E is perpendicular to B
D) E, v and B are mutually perpendicular to each other and \[v=\frac{E}{B}\]
Correct Answer: D
Solution :
Key Idea: No deflection is observed, if force due to electric field is equal to that due to magnetic field. When a proton enters an electric field E, the electric force acting on it, is \[F=qE\] ... (i) where q is charge and magnetic force when in magnetic field is \[F=qv\,B\sin \theta \] for \[\theta ={{90}^{o}}\] \[F=qvB\] ... (ii) For no deflection, \[qE=qBv\] \[\Rightarrow \] \[v=\frac{E}{B}\] Hence, v, E and B should be mutually perpendicular to each other.You need to login to perform this action.
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