Electric Field of Moving Charge: Effects on Distance

In summary: According to that, the field at a distance x from a point charge q decreases with the square of the distance, so at a distance of 2x from q, the field is only 1/4 of what it was at 1x. In summary, the field at a distance x from a point charge decreases with the square of the distance.
  • #1
jartsa
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137
First I stand next to a point charge, then I start moving away or towards the charge, which causes the charge to be further away from me according to me (my ruler contracts according to an inertial observer), and as electric field of a point charge decreases with distance, the electric field caused by the charge decreases at my position according to me.

Is that above thing right or wrong?
 
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  • #2
jartsa said:
then I start moving away or towards the charge,
So which one?

jartsa said:
which causes the charge to be further away from me according to me (length contraction)
How would length contraction increase the distance to the charge?
 
  • #3
A.T. said:
So which one?

Let's study both cases, first the easier one, whichever that is.

How would length contraction increase the distance to the charge?

Simple case: Bell's spaceships. Distance increases according to accelerating spaceships.
Complicated case: Bell's spaceships, but one spaceship is out of fuel, but that does not prevent the other spaceship from observing the Bell's spaceship type of change of distance.
 
  • #4
jartsa said:
Bell's spaceships, but one spaceship is out of fuel, but that does not prevent the other spaceship from observing the Bell's spaceship type of change of distance.
If one ship doesn't accelerate (corresponding to the charge in your question?), the one behind it will crash into it. That is hardly an increase in distance.
 
  • #5
You're forgetting the relativity of simultaneity. Put yourself at the origin and the charge at x=X. At time t=0 you accelerate instantaneously to velocity v. Plug the numbers into the Lorentz transforms. Yes, at t=0 the charge is at ##x'=\gamma X##. However, at t'=0, which is your current simultaneity convention, it is at ##x'=X/\gamma## - closer to you. For non-instantaneous acceleration you'd have to specify an acceleration profile to figure out how far you and the charge move during your acceleration phase.

You need to take a look at the electromagnetic tensor (see for example equation 1.58 in Carroll's GR notes - apologies for lack of link, but my phone is not cooperating with linking today) to determine what field you will see.
 

1. What is an electric field?

An electric field is a region around a charged particle or object where a force is exerted on other charged particles. It is represented by electric field lines, which indicate the direction of the force at different points in space.

2. How does a moving charge affect the electric field?

A moving charge creates a magnetic field, which interacts with the electric field to produce an electromagnetic field. This changes the direction and strength of the electric field in the vicinity of the moving charge.

3. What is the effect of distance on the electric field of a moving charge?

The electric field of a moving charge decreases with distance according to the inverse square law. This means that as the distance from the charge increases, the electric field strength decreases at a rate of 1/r², where r is the distance from the charge.

4. How does the direction of motion affect the electric field of a moving charge?

The direction of motion of a charge affects the direction of the electric field it produces. If the charge is moving parallel to the direction of the electric field, the field will be strengthened. If the charge is moving perpendicular to the electric field, the field will be weakened.

5. Can the electric field of a moving charge be shielded?

Yes, the electric field of a moving charge can be shielded by surrounding the charge with a conductive material. This material will absorb the electric field and prevent it from affecting other objects outside of the shield.

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