Consider a charged particle moving through a region in which the electric field

Question

Consider a charged particle moving through a region in which the electric field is perpendicular to the magnetic field, with both fields perpendicular to the initial velocity of the particle (see figure below). Such a device is called a velocity selector because for one particular value of the particle speed vselect the particle will travel straight through the device without being deflected, whereas particles with speeds that are either less than or greater than vselect will be deflected. Consider a case with E = 470 V/m and B = 0.26 T.

Consider a charged particle moving through a region in which the electric field is perpendicular to the magnetic field, with both fields perpendicular to the initial velocity of the particle (see figure below). Such a device is called a velocity selector because for one particular value of the particle speed vselect the particle will travel straight through the device without being deflected, whereas particles with speeds that are either less than or greater than vselect will be deflected. Consider a case with E = 470 V/m and B = 0.26 T. When protons are used, what speed is selected? What is the speed selected for Ca2+ ions? If you were to use your selector with F? ions, what change would be necessary?

Explanation / Answer

The particle would travel straight at the velocity where the Electric force and the Magnetic forces are equal.

F_E=qE

F_B = qvB

The condition is F_E = F_B

Thus, v = E/B = 470/0.26= 1807.69 ms

b) The speed selected is the same for Ca2+ as well because v depends only on E and B. In fact, that's the job of the

velocity selector! To select the same velocity irrespective of the particle moving through it.

v 1807.69 m/s

c)If F- ions were to be used then, the Magnetic field has to point in the opposite direction since the Electric field would change its direction to the case of the protons/Calcium ions.

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---

---

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