Draw the orientation of electric dipole
moment p in a uniform electric field
Such that the dipole experiences
(0) Maximum torque
Minimum torque
Answers
Explanation:
Dipole moment Torque
Expression for Torque experienced by a dipole:
The force on charge +q = FA = qE along the direction of vector E
The force on charge –q = FB = qE opposite to the direction of vector E
As these two forces are equal, opposite and parallel so they form a couple
We know that Torque т = Force * Arm of the couple
T = Force X Arm of couple
= F X AB sin Ɵ
= qE X AB sin Ɵ
= qE X 2a sin Ɵ
= (q X 2a) E sin Ɵ
= pE sin Ɵ where p is the dipole moment
= vector p X vector E
Vector form: The expression for torque is vector form is given below:
T = vector p X vector E = pE sin Ɵ
Where p is the dipole moment and E is the uniform Electric field
Case 1: When Ɵ is 900 then Torque is maximum and is equal to pE which means the dipole moment should be perpendicular to the direction of the uniform electric field E.
Case 2: When Ɵ is 00, then Torque is minimum. It is equal to 0 as sin 0 is zero which means the dipole moment should be parallel to the direction of the uniform electric field E.
Case 3: When Ɵ is 300, then Torque is pE/2. It is equal to pE/2 as sin 300 is half which means the dipole moment should be at an angle 300 to the direction of the uniform electric field E.
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