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GR8677 #25
Problem
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Electromagnetism$\Rightarrow$}Lorentz Force

Recall the Lorentz Force, $\vec{F}=q(\vec{E}+\vec{v}\times\vec{B})$.

$\vec{E}$ and $\vec{B}$ are parallel. The particle is released from rest, so the Electric force would propel it. The resulting velocity would be parallel to the electric field, but since the magnetic field is also parallel to that, there would be no magnetic force contribution. The particle thus goes in a straight line.

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FutureDrSteve
2011-10-29 15:02:56
I did this one qualitatively using the right-hand rule. To find the force the B-field exerts on the particle, I first reasoned that the E-field would propel it on a vector parallel to the E-field. Pointing my fingers in that direction, it's impossible to curl them towards the B-field, since they're parallel. Therefore, the B-field doesn't act on the particle, and it should continue on its straight-line path.
ME
2009-10-11 16:16:13
Could it be that on GR9677: #86 you meant cycloid instead of helical as in choice B instead of C? Thank you so much for your site. I love it!
 LAStew2011-09-12 17:11:19 You mean answer (D)
a19grey2
2008-11-02 22:23:12
Note that if the fields were perpendicular to each other the electron would drift in a helical pattern as in choice (C). It seems ETS likes questions of this type (see: GR9677: #86)

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