Electric Potential Ranking & E Field Direction: Homework Help

[sasuke07]

Homework Statement

1.Rank the electric potential at the four points A, B, C, and D from greatest to least?
2.The E Field at C points which way?
3.The force on a -4 nC charge placed at A is in what direction?

Homework Equations

no equations needed.

The Attempt at a Solution

1. when i was ranking their strength i thought the farther they were the stronger they were. But now i am thinking the closer they are to the charges the stronger they will be. I think the ranking is B, A, C=D. Could someone tell me if this is right or wrong.
2. I thought that C will be pointing to the top right as its on the 15+line and positive pushes away. But that was wrong. Any suggestions?
3. I thought it would point to the bottom left because negative would be attracted to the +15 but again that was wrong. Could some help on this.

 

[SammyS]

Homework Statement

1.Rank the electric potential at the four points A, B, C, and D from greatest to least?
2.The E Field at C points which way?
3.The force on a -4 nC charge placed at A is in what direction?

Homework Equations

no equations needed.

The Attempt at a Solution

1. when i was ranking their strength i thought the farther they were the stronger they were. But now i am thinking the closer they are to the charges the stronger they will be. I think the ranking is B, A, C=D. Could someone tell me if this is right or wrong.
2. I thought that C will be pointing to the top right as its on the 15+line and positive pushes away. But that was wrong. Any suggestions?
3. I thought it would point to the bottom left because negative would be attracted to the +15 but again that was wrong. Could some help on this.

For #1:
They're asking about the electric potential, not the electric field.

For #2 & #3:

How is the direction of the electric field related to equi-potential lines ?

 

[sasuke07]

1. okay, but do you think my rating is correct. strongest to weakest. as well as the general thought process.
2. No idea, i don't really know what i was thinking. Could you tell me how to figure out the direction, maybe an example. Thanks

 

[SammyS]

1. okay, but do you think my rating is correct. strongest to weakest. as well as the general thought process.
2. No idea, i don't really know what i was thinking. Could you tell me how to figure out the direction, maybe an example. Thanks

#1: No. The Electric field is stronger where the equipotential lines are closer together. This asks you to rate the Electric potential from greatest to least.

This ranking has nothing to do with the spacing of the equipotential lines.

#2: \displaystyle V_b-V_a=-\int_a^b \ \vec{E}\cdot\vec{d\ell} \,. So, if \vec{E} is perpendicular to \vec{d\ell}, what does that say about V_b - V_a ?