Physics

If $P$ be the dipole moment and $E$ be the electric field then the potential energy of a dipole is given by:

$W=P.E.cosθ$

Now, given: $P.E.cos60_{o}=2×10_{−19}J$

Then, $P.E=4×10_{−19}J$

Now, the work done to move the dipole further by $30_{o}$,

$W=P.E.cos90_{o}−P.E.cos60_{o}$$=0−(4×10_{−19}×21 )J$

or, $∣W∣=2×10_{−19}J$

The torque experienced by a dipole in an electric field E is $p ×E$

Maximum torque $=pE=qaE=10_{−6}×0.02×10_{−5}=2×10_{−13}Nm$

ExampleDefinitionsFormulaes