Moving Charges and Magnetism - Result Question 17
17. In a certain region of space electric field $\vec{E}$ and magnetic field $\vec{B}$ are perpendicular to each other and an electron enters in region perpendicular to the direction of $\vec{B}$ and $\vec{E}$ both and moves undeflected, then velocity of electron is
[2001]
(b) $\vec{E} \times \vec{B}$
(d) $\vec{E} \cdot \vec{B}$
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Answer:
Correct Answer: 17. (a)
Solution:
- (a) Electron moves undeflected if force exerted due to electric field is equal to force due to magnetic field.
$q|\vec{v} | \vec{B}|=q|\vec{E}| \Rightarrow|\vec{v}|=\frac{|\vec{E}|}{|\vec{B}|}$
