JEE Main2017PhysicsElectrostaticsActual
An electric dipole has fixed dipole moment p → , which makes angle θ with respect to x - axis. When subjected to an electric field E → 1 = E i ^ , it experiences a torque T → 1 = τ k ^ . When subjected to another electric field E → 2 = 3 E 1 j ^ it experiences a torque T → 2 = - T → 1 . The angle θ is:
Options
- A90 o
- B30 o
- C45 o
- D60 o
Correct answer
D. 60 o
Step-by-step solution
P → = P cos ⁡ θ i ^ + P sin ⁡ θ j ^ T → = P cos ⁡ θ i ^ + P sin ⁡ θ j ^ × E i ^ = - P E sin ⁡ θ k ^ T → 2 = P cos ⁡ θ i ^ + P sin ⁡ θ j ^ × 3 E j ^ =   3 P E cos ⁡ θ k ^ T → 2 =   - T → 1 ∴         sin ⁡ θ =   3 cos ⁡ θ ∴         tan ⁡ θ =   3 ∴       θ = 60 o