Charged Particles in Magnetic Fields

Click For Summary
An ionized deuteron with a positive charge passes through a velocity selector with electric and magnetic fields of 8 kV/m and 40 mT, respectively. The forces acting on the particle are described by F = qE for the electric field and F = qvB for the magnetic field. By equating these forces, the speed of the ion can be calculated using the formula v = E/B, resulting in a speed of 320 m/s. There is some confusion in the discussion regarding the multiplication of E and B, with suggestions to clarify the calculations. Ultimately, the correct approach to find the speed involves using the relationship v = E/B directly.
predentalgirl1
Messages
61
Reaction score
1
1. An ionized deuteron (a particle with a + e charge) passes through a velocity selector whose perpendicular magnetic and electric fields have magnitudes of 40 mT and 8.0 kV/m, respectively. Find the speed of the ion



2. When a charge particle moves in a velocity selector, both electric field and magnetic field are there.

Any charged particle in an electric field will feel a force proportional to the charge and field strength such that F = qE , where F is force, q is charge, and E is electric field. Similarly, any particle moving in a magnetic field will feel a force proportional to the velocity and charge of the particle. The force felt by any particle is then equal to F = qv X B , where F is force, q is the charge on the particle, v is the velocity of the particle, B is the strength of the magnetic field, and X is the cross product. In the case of a velocity selector, the magnetic field is always at 90 degrees to the velocity and the force is simplified to F = qvB in the direction described be the cross product.

F = qE and F = qvB

So, qE = qvB

V = E/B

Setting the two forces to equal magnitude in opposite directions it can be shown that V = E/B . Which means that any combination of electric (E) and magnetic (B) fields will allowed charged particles with only velocity (v) through.





3. E = 8 KV/m = 8 x 103 V/m

B = 40 mT = 40 x 10-3 T

V = 8 x 103 x 40 x 10-3

V = 320 m/sec

(Ans)

 
Physics news on Phys.org
predentalgirl1 said:
Any charged particle in an electric field will feel a force proportional to the charge and field strength such that F = qE , where F is force, q is charge, and E is electric field. Similarly, any particle moving in a magnetic field will feel a force proportional to the velocity and charge of the particle. The force felt by any particle is then equal to F = qv X B , where F is force, q is the charge on the particle, v is the velocity of the particle, B is the strength of the magnetic field, and X is the cross product. In the case of a velocity selector, the magnetic field is always at 90 degrees to the velocity and the force is simplified to F = qvB in the direction described be the cross product.

F = qE and F = qvB

So, qE = qvB

V = E/B

Setting the two forces to equal magnitude in opposite directions it can be shown that V = E/B . Which means that any combination of electric (E) and magnetic (B) fields will allowed charged particles with only velocity (v) through.





3. E = 8 KV/m = 8 x 103 V/m

B = 40 mT = 40 x 10-3 T

V = 8 x 103 x 40 x 10-3

V = 320 m/sec

(Ans)


Why have you multiplied E and B?

(I really don't feel that you should copy and paste almost the entire page from Wikipedia, along with the grammatical and spelling mistakes. Write it yourself.)
 
Shooting star said:
Why have you multiplied E and B?

(I really don't feel that you should copy and paste almost the entire page from Wikipedia, along with the grammatical and spelling mistakes. Write it yourself.)


If I should not multiply E and B, what
should I do instead to get the correct answer?
 
predentalgirl1 said:

F = qE and F = qvB

So, qE = qvB

V = E/B

This is from your post. What do you think you should do to get v?
 
Given that B =40 x 10 ^-6
E = 8000 V/m

have Bev = eE

v = E/B

v= 8000/ 40 x 10^-6
v= 2 x 10^8m/s
 
predentalgirl1 said:
Given that B =40 x 10 ^-6
Is the value of B you have used here is correct?
 
Thread 'Correct statement about size of wire to produce larger extension'
The answer is (B) but I don't really understand why. Based on formula of Young Modulus: $$x=\frac{FL}{AE}$$ The second wire made of the same material so it means they have same Young Modulus. Larger extension means larger value of ##x## so to get larger value of ##x## we can increase ##F## and ##L## and decrease ##A## I am not sure whether there is change in ##F## for first and second wire so I will just assume ##F## does not change. It leaves (B) and (C) as possible options so why is (C)...

Similar threads

Replies
1
Views
2K
Replies
12
Views
2K
Replies
14
Views
3K
  • · Replies 4 ·
Replies
4
Views
545
  • · Replies 31 ·
2
Replies
31
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 1 ·
Replies
1
Views
813
  • · Replies 25 ·
Replies
25
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K