Question
Sun September 27, 2009 By:

I wanted to know that potential energy is actually the work done to rotate the dipole from an initial angle a to some other angle

Why is the potential energy min. for an electric dipole when torque is max. in a const. electric fie

Expert Reply
Thu December 17, 2009

HI dear,

In case of a diploe,

charge q1 = +q and charge q2 = -q, if the external field be along th x direction, and the origin be at the center of the dipole, then the potential energy of the dipole is:

qv(r1) - qv(r2)-q2/(4π∈o2a)

The potential differnce between q1 and q2 is the work done in moving a unit positive charge against field..

v(r1) - v(r2) = - E. 2 a cos q

Negative potential indicates the decrease in potential in the direction of field.

Dipole has minimum potential energy when alligned with the field and a dipole in a uniform field experiences a torque. Thus, if dipole can fritter away its potential energy, torque will allign the dipole in the direction of the external field therby making its potential to a minimum .

Hope this helped.

Regards

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