Finding the Trajectory of a Test Charge in an Electric Field

In summary, the conversation discusses the placement of a test charge in an electric field and how to find its trajectory. The problem is that the formula used for finding the trajectory in a gravitational field assumes a uniform field, but in this case, no such approximation can be made. There is a discussion about whether to use a differential equation or a method like Newton's method. It is also mentioned that in the case of two point charges, the acceleration is along the line connecting the two charges. The conversation ends with the realization that a differential equation is needed to solve the problem.
  • #1
tickle_monste
69
1
Let's say I were to place a test charge, q0, in a standard electric field E = k*q1/(r^2).
How would I find the trajectory of the charge? I have been trying the method used for finding the trajectory in a gravitational field, but I believe the problem is that that formula (Gm1m2/(r^2)) assumes a uniform field, whereas in this smaller scale problem, no such approximation can be made. I'm not sure whether I should be looking for a differential equation or something like Newton's method or what.
 
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  • #2
Hello

Test charges would keep still on the points during observation of electric fields by measuring the applied force/charge. In this sense trajectory of test charge does not make good sense to me. If you are interested in motion of charges, two body problem under square inverse law with parameters e1,e2,m1,m2, should be your case. I believe scale problem does not matter in square inverse law.

Regards.
 
  • #3
I think you're talking about a point charge placed into a field generated by another point charge. The direction of the resulting force is along the line connecting the two point charges, therefore the resulting acceleration is along that line.

Gm1m2/r^2 is not for a uniform gravitational field. It's for the force between two point masses, which is a radial set of directions for field lines.
 
  • #4
Well the problem I get when I don't assume a uniform field is that the amount of acceleration is a function of position. But the position is a function of acceleration which is a function of position etc.

*EDIT* so yea, I realize now that I'm looking at a differential equation
 
Last edited:

1. What is a test charge?

A test charge is a small, hypothetical charge used to measure the strength and direction of an electric field. It is typically a positive charge with a small magnitude, and is placed at various points within the electric field to determine the force experienced at that point.

2. How is a test charge used to measure electric fields?

The test charge is placed at a specific point within the electric field, and the force experienced by the test charge is measured. This force is then used to calculate the strength and direction of the electric field at that point. By moving the test charge to different points within the electric field, the entire field can be mapped out.

3. Why is a test charge necessary?

A test charge is necessary because it allows us to measure and understand the properties of an electric field without disturbing or changing the field itself. Since the test charge has a small magnitude, it does not significantly alter the electric field, allowing for accurate measurements.

4. What is the relationship between test charge and electric field?

The force experienced by the test charge is directly proportional to the strength of the electric field at that point. This means that the larger the electric field, the greater the force experienced by the test charge. The direction of the force also indicates the direction of the electric field at that point.

5. Can a test charge be negative?

Yes, a test charge can be negative. While a positive test charge is typically used, a negative test charge can also be used to measure the electric field. However, the force experienced by a negative test charge will be in the opposite direction of a positive test charge, which should be taken into account when calculating the strength and direction of the electric field.

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