# What is the electrical potential at point P?

1. Mar 8, 2017

### ikihi

1. The problem statement, all variables and given/known data

Three point charges of +6.00 μC, +4.00
μC, and +6.00 μC are placed along the x-axis 0.200 m above the +4.00 μC charge as shown in the figure below. What is the electrical potential at point P (relative to infinity) due to these charges?

Diagram:

https://pbs.twimg.com/media/C6cPxGfU0AA9QMB.jpg:large [Broken]

2. Relevant equations

Vp = V1 + V2 + V3
Vp= $\frac {kQ} {r^2}$ + $\frac {kQ} {r^2}$ + $\frac {kQ} {r^2}$

3. The attempt at a solution

Vp= $\frac {kQ} {r^2}$ + $\frac {kQ} {r^2}$ + $\frac {kQ} {r^2}$

Vp= 8.99 x109 ⋅ 6 x 10-6 / 0.2832 + 8.99 x109 ⋅ 4.00 x 10-6 / 0.2002 + 8.99 x109 ⋅ 6 x 10-6 / 0.2832

Vp = 2.24 × 106 V

Last edited by a moderator: May 8, 2017
2. Mar 8, 2017

### Arman777

Your potential Energy defition is wrong It cannot be $V_p=\frac {kQ} {r^2}$.Think about it.

3. Mar 8, 2017

### ikihi

I'm not sure what other equation it would be. This is electrical potential (voltage). I know there are 3 charges and there is a distance r for each of them to the point P.

4. Mar 8, 2017

### haruspex

You are confusing it with the formula for the field. Your equation is dimensionally wrong.

5. Mar 8, 2017

### ikihi

Oh okay I see my error. I squared the r, when it shouldn't be.

6. Mar 8, 2017

### haruspex

Right.
Do you get the right answer now, or can't you tell yet?

7. Mar 8, 2017

### ikihi

Yes I got the right answer. Thanks.