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Two small identical electrical dipoles AB and CD each of dipole moment 'p' are kept at an angle of120 ^(@)as shown in What is the resultant dipole moment of this combination ? If this system is subjected to electric field. oversetto E directed along +X direction ,what will be the magnitude and direction of the torque acting on this? (##U_LIK_SP_PHY_XII_C01_E09_029_Q01.png" width="80%"> |
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Answer» Solution :As shown in let two identical electric dipoles AB and CD are kept at an ANGLE ` theta= 120 ^(@) ` ,where their dipole moment have magnitude `""| oversetto (p_A) |=|(oversetto p_C)| =p` The resultant dipole moment subtend an angle ` (theta)/(2)= 60 ^(@)` from EITHER of two dipoles ` oversetto (p_A)or oversetto (p_B) ` Therefore `oversetto (p_R) ` subtend an angle `30^(@) `from +X direction If the system is SUBJECTED to electric field `oversetto E ` directed along +X direction, the torque acting on the system is ` oversetto tau = oversetto (p_R) xx oversetto E ` Thus ,the magnitude of torque is ` | oversetto (tau)| =pE sin 30^(@) =(1)/(2)pE `and the torque is directed into the plane of paper i.e., the torquetends to align the system along the direction of electric field `oversetto E ` ` (##U_LIK_SP_PHY_XII_C01_E09_029_S01.png" width="80%"> |
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