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# Electric Field due to a Dipole

" To punish me for my contempt for authority, fate made me an authority myself"
Albert Einstein

- An electric dipole consists of two point charges of equal magnitude, but opposite sign, separated by a short distance.

- The dipole is electrically neutral, but due to the separation of its charges gives rise to an electric field in its vicinity.

- The electric field at the "field point" is given by E = E+q + E-q. Note that in adding the two electric fields the y-component cancels leaving only an x-component given by,

> where R is the distance from the centre of the dipole to the field point and the approximation is valid when r and R are almost equal. In this case the dimension of the dipole (a) is small compared to the field point distance.

- p (=2aq) is called the electric dipole moment. It's actually a vector pointing from the negative to the positive charge in the dipole so that,

- Many molecules have charge distributions which can be approximated as an electric dipole, water being one of the most common.

"How many Astronomers does it take to change a light bulb ?
None, astronomers prfeer the dark"

Dr. C. L. Davis
Physics Department
University of Louisville
email: c.l.davis@louisville.edu