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# Electric Dipole in an External Electric Field

" When you look at yourself from a universal standpoint, something inside always reminds or informs you that there are bigger and better things to worry about."
Albert Einstein

- We have already considered the electric field created by an electric dipole. Now we consider the behavior of an electric dipole placed in a uniform (constant) electric field.

- Note that since the force on each of the charges are equal in magnitude but opposite in direction there is no net force on the dipole.

- However, since the two forces are not concurrent, there is a non-zero torque about the center of the dipole given by,

- Using the definition of the work done by a torque (rotational force), it can be shown that the electrical potential energy stored by a dipole in an external field is given by,

- A dipole placed in a uniform electric field will rotate until it is aligned "-" to "+" along the field - this is the lowest energy configuration.

- If the external field is not uniform, the net force will not be zero.

What is a quantum particle? The dreams that stuff is made of!

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