- #1

Oribe Yasuna

- 43

- 1

## Homework Statement

In the simple mass spectrometer shown in the figure below, positive ions are generated in the ion source. They are released, traveling at very low speed, into the region between two accelerating plates between which there is a potential difference Δ

*V*. In the shaded region there is a uniform magnetic field B

*M*, which travels through the accelerating plates into the magnetic field region, and hits the ion detector as shown.

Determine the appropriate magnitude and direction of the magnetic field B

*M*and

*q*, where

*q*is the charge on an ion).

Magnitude B = ?

direction = ?

## Homework Equations

F

_{mag}= dp/dt

_{mag}= qvB

dp/dt

_{mag}= p(v/R) = p(omega), p = ymv

omega = q_mag * b / (ym)

## The Attempt at a Solution

deltaV (I don't know what to do with electrical potential)

M (mass)

q (charge)

d/2 = R (radius)

v << c, y = 1, p = mv (approximation)

F

_{mag}= dp/dt

_{mag}

qvB = p(v/R)

qvB = p(v/(d/2))

qB = p/(d/2))

B = p/(d/2))/q

B = 2p/dq, p = mv (approx.)

B = 2Mv/dq

This is wrong, probably because I'm not given velocity. However, I don't know how to get magnetic field without velocity? I think the problem is I don't know what to do with electric potential.

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