Consider the passage of a horizontal electron beam through a velocity selector,

Question

Consider the passage of a horizontal electron beam through a velocity selector, where the electric field ~E points downward and the magnetic field ~B points into the paper.

Based on the Lorentz force law, what is the critical speed vc (the speed at which the horizontal electron beam is not deflected)?

007 (part 2 of 2) 10.0 points
If the speed of the electrons is greater than the
critical speed, the trajectory of the electron
beam will be

1. deflected upward.
2. deflected upward and into the paper.
3. deflected upward and out of the paper.
4. deflected downward.
5. deflected into the paper.
6. undeflected.
7. deflected out of the paper.
8. deflected downward and out of the paper.
9. deflected downward and into the paper.

Explanation / Answer

From the lorentz force law Force from the electric field = qE Force from magnetic field = Bqv Equating these 2 equations : qE= Bqv --> v = E/B Therefore the answer is (4) using Flemming's left hand rule, the electrons will be deflected down the page but remain on the plane Answer ( 4)

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.