Question
Tue June 05, 2012 By: Awais Rauf
 

An electric dipole is placed in a uniform electric field: (a) Show that no translatory force acts on it (b) Derive an expression for the torque acting on it. (c) Find work done in rotating the dipole through 180 degree

Expert Reply
Tue June 05, 2012
torque= mag of either force x perpendicular distance b w the line of action of force

torque= qe x bc

= qe d sin(electric dipole p= qd ) (since bc= d sin o )

torque= PE sin o

An electric dipole will naturally have its dipole moment p aligned to the external electricfield E.  the equilibrium configuration will have ?=0.When the dipole is not aligned, an external work W will have to be done on the dipole(from the external electric field) to bring it from the rest position to a given angle ?:UP = ?W = R?0 ?d?UP is the potential energy associated with the work done by the conservative elec-trostatic force, which causes the torque ? . The infinitesimal work done by the electrostaticforce is dW = ?d? = ?pE · sin(?)d?.? UP = pE · (? cos(?)|?0) = ?pE(·cos(?) ? ·cos(0)).

Ask the Expert