# Homework Help: Having trouble finding the potential between two positive point charges.

1. Jan 29, 2013

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

How to find the potential between two positive point charges?

I don't know where I'm going wrong.

==I am adding V_1 and V_2. converted mC to C, cm to m, correct value of k.

V1= kq1 / r1
v2= kq2/ r2.

==I am adding both of these, but I'm not getting the correct answer.

===Problem:

A point charge of q1 = 2.37 µC is 44 cm from a charge of q2 =26.4 µC. Where is the electric field zero? What is the value of the potential there?
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electric field is zero at 0.101m (correct answer).

I have r1= .101m and r2= .44m - .101= .34m.

I'm using the correct value of k.

== The answer is given as 2.34 * 10^6 V.

Can you help me find out where I'm doing wrong?

2. Jan 29, 2013

### haruspex

We cannot tell where you are going wrong if you do not post all your working.

3. Jan 29, 2013

Edit: The potential at the point is equal to the sum of the two potentials of the two point charges.

V= kq_1 / r_1 + kq_2 /r_2

V= (9*10^9 Nm^2/C^2)* (2.37 * 10^-6 C)/ .101m + (9*10^9 Nm^2/C^2)*(26.4*10^-6 C) / .34m = 9.10*10^5 V.

The correct answer is 2.34 *10^6 V.

I don't know what I'm doing wrong.

4. Jan 29, 2013