Electric Field Electric potential and Coulomb Force

1. The diagram shows the electric field due to a point charge. Determine if the point charge is positive or negative. Find the location of the charge. Draw it on the diagram. (See diagram)

2. Can you assign charges for the following four cases, so that these forces are correct? (See diagram)

3. Figure below shows three points in the vicinity of two point charges. Rank in order the potentials V1, V2 and V3. (See diagram)

Solution is attached in a file called "ConceptualQuestions.doc". The text part of this file is copied and pasted below.
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(1)

We cannot say if the charge is + or -.

Reason:

Lets see how the electric field is defined. Electric field at a point A due to a point charge q is the force on a +1 C charge located at point A.

In the above diagram, if you place a +1 C charge,

In order to produce the Electric field in the given direction, a positive charge +q should be placed some where to the left of point A, or a negative charge -q should be placed some where to the right of point A.

In other words, this filed E = 900 N/C could have been produced by either a + charge to the left or a - charge to the right. Therefore, we cant say exactly if it is + or - charge which caused this E field.

(b)

We can say if these fields were produced by a positive or a negative charge.

Reason

We can determine that this charge ...

Solution Summary

Solutions are provided in a 6-page word document along with several diagrams. Questions are answered with very clear explanations so that student can learn to do similar problems in the future.

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