Question about the motion charges moving within an electric field

In summary, according to the OCW, the motion of a charge within an electric field does not follow the field lines. The path of the charge depends on the ratio of the charge to the mass of the object.
  • #1
Excalibur1152
11
0
I've almost certain that I have read/ seen from MIT's OCW that the motion of a charge within an electric field does not follow the field lines.

Today my physics teacher said the opposite, that the path of motion of a charge within a field will follow a field line.

Who is right? And why?

EDIT: I meant to put an 'of' in between the 'motion' and 'charges' in the title.
 
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  • #2
If the charge started off with no velocity then it will 'fall' along field lines just the same as a dropped object falls vertically on Earth. If the object was originally moving then it will follow a trajectory, accelerating in the direction of the field lines, and its velocity will always be the (vector) sum of its original velocity and the velocity in the direction of the force due to the field. For a uniform field, the shape of path will be part of a parabola.
 
  • #3
edip2.gif




So if I were to place a (positive) charge on top of one of the field lines ^^^ without giving it an initial velocity, it would never leave the line? It's path would only exist upon the same field line?



(I know that there are an infinite # of lines, but as far as the picture is concerned)
 
  • #4
Excalibur1152 said:
edip2.gif




So if I were to place a (positive) charge on top of one of the field lines ^^^ without giving it an initial velocity, it would never leave the line? It's path would only exist upon the same field line?



(I know that there are an infinite # of lines, but as far as the picture is concerned)

Right - that diagram has made me think again! I was considering, initially, straight field lines (point source or between plates).

If the lines are curved then you would expect the velocity of the charged object, once it had been accelerated at all, would not be parallel to the lines of force so it would move through them and not follow just one line. The degree that it would depart from the line it 'started on' would presumably depend upon the ratio of the charge of the object to its mass. If it had no mass then it would follow the line.
 
  • #5
sophiecentaur said:
Right - that diagram has made me think again! I was considering, initially, straight field lines (point source or between plates).

If the lines are curved then you would expect the velocity of the charged object, once it had been accelerated at all, would not be parallel to the lines of force so it would move through them and not follow just one line. The degree that it would depart from the line it 'started on' would presumably depend upon the ratio of the charge of the object to its mass. If it had no mass then it would follow the line.

Indeed, if the field lines are straight, then the charge should only move along the field lines.

If the charge does have mass, it gains kinetic energy, and so when the field line curves, then work has to be done over a distance to "change" the path of motion? Wouldn't this distance be the distance that the charge moves out of the field line? (maybe not that simple, but hopefully you can still follow my logic).

As an example, if you put a positive charge with mass right between the two charges on the dipole I posted earlier (but imagine that both are positive charges, so three positive charges total), but moved it closer to one of the charges, wouldn't it oscillate between them? If it did that, then wouldn't it be moving against a field line?
Much thanks for responding to my posts.
 
  • #6
It's a conservative field so kinetic plus potential energy will be constant, so yes it could go 'uphill' at times.
 

1. What is an electric field?

An electric field is an area surrounding an electrically charged particle or object in which other charged particles experience a force.

2. How do charges move within an electric field?

Charges move within an electric field due to the presence of the electric force. This force causes the charges to accelerate and move in the direction of the electric field lines.

3. What is the relationship between charge and electric field?

The electric field is directly proportional to the charge and inversely proportional to the distance between the charges. This means that as the charge increases, the electric field strength also increases, but as the distance between the charges increases, the electric field strength decreases.

4. What factors affect the motion of charges within an electric field?

The motion of charges within an electric field is affected by the strength of the electric field, the magnitude of the charge, and the distance between the charges. Other factors such as the presence of other electric charges or magnetic fields can also affect the motion of charges.

5. How is the motion of charges within an electric field used in technology?

The motion of charges within an electric field is utilized in various technologies such as electric motors, generators, and capacitors. It is also used in particle accelerators, where electric fields are used to accelerate charged particles to high speeds.

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