How can the force NOT be zero here?

  • Thread starter Thread starter flyingpig
  • Start date Start date
  • Tags Tags
    Force Zero
Click For Summary
SUMMARY

The discussion centers on the interpretation of forces in the context of a velocity selector as described in the textbook "Physics for Scientists and Engineers" by Serway and Beichner. The participants clarify that while the vector sum of forces appears to be zero in the figure 29.23, this is only true for particles with a specific velocity defined by the equation v=E/B. The Lorentz force can be zero in this specific case, but it is not universally zero for all scenarios. The velocity selector is designed to filter charged particles based on their velocity, allowing only those that meet the criteria to pass through unimpeded.

PREREQUISITES
  • Understanding of the Lorentz force and its implications in electromagnetic fields.
  • Familiarity with the concept of velocity selectors in physics.
  • Knowledge of the relationship between electric field (E), magnetic field (B), and velocity (v) in charged particle dynamics.
  • Ability to interpret vector diagrams and force summation in physics contexts.
NEXT STEPS
  • Study the Lorentz force in detail, including its applications in charged particle motion.
  • Research the design and function of velocity selectors in mass spectrometry.
  • Explore the mathematical derivation of the relationship v=E/B and its significance in particle physics.
  • Examine case studies where the net force is zero and the implications for particle trajectories.
USEFUL FOR

Students of physics, educators teaching electromagnetism, and professionals working in fields related to particle physics and mass spectrometry will benefit from this discussion.

flyingpig
Messages
2,574
Reaction score
1
Physics news on Phys.org
What page in the book? I don't se any pages labeled 17 and 18.
 
In the pdf
 
I loaded the pdf. It starts on page 894.
 
There are 32 pages
 
Are you talking about the "Active figure 29.23"?
If so you're right that the total force is zero, but I see nowhere why it couldn't be zero.

They talk about the Lorentz force which isn't necessarily zero and is precisely zero in the special case of the figure 29.23. It can of course be zero in other (hypothetical at least) situations.

Where did you read that the force is NOT zero? What page exactly?
 
I didn't read anywhere that it isn't zero, the picture tells me. The force is equal in magnitude and opposite direction
 
Just a bit further down the same page, the point is that the velocity selector allows a charged particle with a certain velocity to shoot straight down the finely tuned system between the plates and in the magnetic field unimpeded. Presumably, if it veers off the middle line just a bit, the particle will be "discarded" if you will. Then, a slit at the end of the velocity selector will allow those particles that are of the certain velocity (v=E/B...and you can tune your velocity selectors E and B fields to get that specific velocity) to continue onward (such as in a mass spectrometer where you want to be sure of the initial velocity...stick a velocity selector in front of your mass spectrometer region, like in the next figure).

The net force is only 0 for those particles with v=E/B.
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
Replies
2
Views
6K
Replies
17
Views
10K
  • · Replies 5 ·
Replies
5
Views
3K
Replies
2
Views
10K
  • · Replies 15 ·
Replies
15
Views
7K
  • · Replies 5 ·
Replies
5
Views
7K
  • · Replies 0 ·
Replies
0
Views
2K
  • · Replies 28 ·
Replies
28
Views
4K
  • · Replies 27 ·
Replies
27
Views
11K