Mass spectrometer problem -- Need help

Click For Summary

Homework Help Overview

The problem involves a mass spectrometer utilizing a velocity selector with a parallel plate capacitor and a uniform magnetic field. Participants are tasked with determining the radius of motion for ions of a specified mass and charge based on given electric and magnetic field strengths.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants discuss the relationship between electric and magnetic forces acting on ions in the spectrometer. There are attempts to apply relevant equations, but some participants question the correctness of the formulas used and the interpretation of forces involved.

Discussion Status

There is ongoing exploration of the problem, with participants providing attempts at solutions and questioning the application of formulas. Some guidance is offered regarding the identification of forces acting on the ions, but no consensus has been reached on the correct approach.

Contextual Notes

Participants note that the problem may involve misunderstandings about the forces acting on the ions, particularly in relation to the electric field and the charge of the particle. There is also mention of the need to clarify the correct application of the equations provided.

Ryan Gibbons
Messages
2
Reaction score
0

Homework Statement



A mass spectrometer is constructed using a velocity selector constructed using a parallel plate capacacitor in a uniform magnetic field Bin. The electric field in the selector is 1003.9 V/m and the magnetic field in that portion of the spectrometer is Bin = 0.998 T. The balanced forces only allow specific velocities through the selector.

http://misterfig.org/pluginfile.php/1936/question/questiontext/8281/18/123907/spect.jpg
The mass of the ions can be found by measuring the radius of the motion when the ions strike point P.
The magnetic field in the circular motion chamber is Bout = 0.807 T.
What is the radius (in millimeters) for an ion of mass 2.66 x 10-26 kg and a charge of +e (1.60 x 10-19 C) ?

Homework Equations


Fm=Fe
BQV=MV^2/R
VQ=MV^2/2

The Attempt at a Solution


VQ=MV^2/2
V=2Q/M= 12030075.19 m/s

BQV=MV^2/R
R=MV/BQ=2.48 m
This is not the correct solution but i cannot figure out how to find the correct one. Please help. Thanks
 
Last edited by a moderator:
Physics news on Phys.org
Ryan Gibbons said:

Homework Statement



A mass spectrometer is constructed using a velocity selector constructed using a parallel plate capacacitor in a uniform magnetic field Bin. The electric field in the selector is 1003.9 V/m and the magnetic field in that portion of the spectrometer is Bin = 0.998 T. The balanced forces only allow specific velocities through the selector.

http://misterfig.org/pluginfile.php/1936/question/questiontext/8281/18/123907/spect.jpg
The mass of the ions can be found by measuring the radius of the motion when the ions strike point P.
The magnetic field in the circular motion chamber is Bout = 0.807 T.
What is the radius (in millimeters) for an ion of mass 2.66 x 10-26 kg and a charge of +e (1.60 x 10-19 C) ?

Homework Equations


Fm=Fe
BQV=MV^2/R
VQ=MV^2/2

The Attempt at a Solution


VQ=MV^2/2
V=2Q/M= 12030075.19 m/s

You apply the wrong formula. What is the electric force on the particle?
Ryan Gibbons said:
BQV=MV^2/R
R=MV/BQ=2.48 m
This is not the correct solution but i cannot figure out how to find the correct one. Please help. Thanks
 
the electric force on the particle is 1.6x10^-19 C
 
Ryan Gibbons said:
the electric force on the particle is 1.6x10^-19 C
No, it is the charge of the particle. What force acts on it due to the electric field of the velocity selector?
 

Similar threads

Charges of ions in a mass spectrometer
  • · Replies 1 ·
Replies
1
Views
2K
Why Ignore the Magnetic Field in a Mass Spectrometer?
  • · Replies 1 ·
Replies
1
Views
2K
Mass spectrometer - no deflection
  • · Replies 14 ·
Replies
14
Views
3K
Circular Motion in a Simple Mass Spectrometer
  • · Replies 4 ·
Replies
4
Views
5K
Mass-to-Charge Ratio of an Ion in Mass Spectrometer
  • · Replies 1 ·
Replies
1
Views
2K
TOF (mass spectrometer) Analyzer Question
  • · Replies 2 ·
Replies
2
Views
2K
How Is Current Calculated in a Mass Spectrometer?
  • · Replies 3 ·
Replies
3
Views
2K
Distance between Isotopes in a mass spec
  • · Replies 8 ·
Replies
8
Views
10K
Speed, force, magnetic flux of an ion?
  • · Replies 13 ·
Replies
13
Views
3K
How Do Ions Achieve Their Velocity in a Mass Spectrometer?
  • · Replies 3 ·
Replies
3
Views
3K