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Question: Answered & Verified by Expert
An electric field of $1000 \mathrm{~V} / \mathrm{m}$ is applied to an electric dipole at angle of $45^{\circ}$. The value of electric dipole moment is $10^{-29} \mathrm{C} \cdot \mathrm{m} .$ What is the potential energy of the electric dipole?
PhysicsElectrostaticsJEE MainJEE Main 2019 (11 Jan Shift 2)
Options:
  • A $-20 \times 10^{-18} \mathrm{~J}$
  • B $-7 \times 10^{-27} \mathrm{~J}$
  • C $-10 \times 10^{-29} \mathrm{~J}$
  • D $-9 \times 10^{-20} \mathrm{~J}$
Solution:
1080 Upvotes Verified Answer
The correct answer is: $-7 \times 10^{-27} \mathrm{~J}$
Potential energy of a dipole is given by $\mathrm{U}=-\overrightarrow{\mathrm{P}} \overrightarrow{\mathrm{E}}$

$=-P E \cos \theta$

[Where $\theta=$ angle between dipole and perpendicular to the field $=-\left(10^{-29}\right)\left(10^{3}\right) \cos 45^{\circ}$

$=-0.707 \times 10^{-26} \mathrm{~J}=-7 \times 10^{-27} \mathrm{~J}$

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