Magnetostatics and Electrostatics

In summary, the conversation discusses how to determine the density of negative charges in a wire when the positive charges are at rest and the negative charges are moving at a certain velocity. It is mentioned that gamma is a ratio and that the concept of conservation of global electric charge must be considered in relativity. The conversation suggests following a different approach suggested by Marco_84 for solving this problem.
  • #1
johanjones190
5
0
Here is the problem, I have no idea how to do this!

(In a single straight wire) If the positive charges (density p+) are at rest, and the negative charges (density p-) move at speed v, show that:

p- = -(p+)*(gamma)^2
 
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  • #2
Is gamma some kind of ratio?

The traveling charges (enclosed current) induces a magnetic field which in turn imposes a force on moving charges, which then must be offset by an electrostatic attraction.
 
  • #3
Yeah gamma = 1/ sqrt(1-v^2/c^2) where v is velocity and c is the speed of light!
 
  • #4
Try to think that the global electric charge must be conserved, and see how in relativity change the volumes by lorentz contraction. then remember that Q=density times volume and you'll get the answer...
 
  • #5
Astronuc said:
The traveling charges (enclosed current) induces a magnetic field which in turn imposes a force on moving charges, which then must be offset by an electrostatic attraction.
for get this approach and go with what Marco_84 suggested. I was thinking something entirely different, not realizing that this was about SR.
 

1. What is the difference between magnetostatics and electrostatics?

Magnetostatics deals with the behavior of stationary or constant magnetic fields, whereas electrostatics deals with stationary or constant electric fields.

2. How do magnetic fields interact with electric fields?

Magnetic fields and electric fields are closely related and can interact with each other. This interaction is known as electromagnetism and is described by Maxwell's equations.

3. How can I calculate the strength of a magnetic field?

The strength of a magnetic field can be calculated using the formula B = μ0I/2πr, where B is the magnetic field strength, μ0 is the permeability of free space, I is the current, and r is the distance from the source of the field.

4. What is the difference between a permanent magnet and an electromagnet?

A permanent magnet is a magnet that retains its magnetic field without the need for an external power source, whereas an electromagnet uses electricity to produce a magnetic field.

5. How can I shield magnetic and electric fields?

Magnetic and electric fields can be shielded using materials with high magnetic permeability and high electrical conductivity, such as iron or copper. These materials can redirect or absorb the fields, reducing their strength.

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