The dipole moment of a water molecule is 6.2 x 10(adsbygoogle = window.adsbygoogle || []).push({}); ^{-30}Cm. Find the potential difference V_{B}- V_{A}between 2 points on the axis of the molecular dipole, where points A and B are 8.2 nm and 5.1 nm respectively from the center. Both points are closer to the positive end.

I used the superposition principle to calculate the potential at each point. so V_{B}= [itex] \frac{kq}{a - 5.1} - \frac{kq}{a + 5.1} [/itex] where a is the distance from each point charge to the center. Also, V_{A}= [itex] \frac{kq}{a - 8.2} - \frac{kq}{a + 8.2} [/itex]. i know that 2aq = 6.2 x 10^{-30}. but now i am having trouble finding a numerical value. when i subtract V_{B}- V_{A}i get these annoying a^{2}- 5.1^{2}and a^{2}- 8.2^{2}in the denominator and i can't seem to get rid of them. my answer is messy and in terms of variables while the book's answer is a number. am i missing a piece of information? any help is greatly appreciated.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Potential difference between 2 points on dipole axis

**Physics Forums | Science Articles, Homework Help, Discussion**