Which charge is at higher potential: q at distance r or 2q at distance 2r from Q?

[wolski888]

Homework Statement

Charge Q is located at the (x,y) origin. q is a distance r in the +x direction from Q. 2q is a distance 2r in the +x direction from Q. Which of q or 2q is at a higher potential? q, 2q, or same.

The Attempt at a Solution

I am thinking that it would depend on Q. Q=0, then the higher potential is at q. But if it wasn't =0? The fact that 2q and q impact each other's potential also makes this problem difficult. Any thoughts?

 

[sandy.bridge]

We know that $$V=\frac{kq}{R}$$, correct? Do all potential calculations at the origin. For example, measure the potential due to q, and 2q at the origin where Q is located.

What do you get?

 

[wolski888]

Wouldn't it be the same for 2q and q? But if you mean add them together than V = kq(squared) / r. No?

 

[sandy.bridge]

Does the question indicate whether Q is positive or negative?

 

[wolski888]

No, it does not.

 

[sandy.bridge]

The sign of Q is the determining factor in this situation.

 

[wolski888]

Then what would be the answer for both cases?