An electric dipole of dipole moment 6.0 × 10⁻⁶ C m is placed in a uniform electric field 1.5 × 10³ N C⁻¹ with its dipole moment along the field. Work done in rotating the dipole through 180° i s ______ mJ.
Physics · Electrostatic · electric dipole and dipole moment
JEE Mains 8 April 2023 Shift 1 Morning Shift

Question

An electric dipole of dipole moment 6.0 × 10⁻⁶ C m is placed in a uniform electric field 1.5 × 10³ N C⁻¹ with its dipole moment along the field. Work done in rotating the dipole through 180° i s ______ mJ.

Physics · Electrostatic · electric dipole and dipole moment

JEE Mains 8 April 2023 Shift 1 Morning Shift

G1 Physics · Accepted Answer

Potential energy of an electric dipole in a uniform field is U = -pE cosθ Initially: θ₁ = 0° U₁ = -pE Finally: θ₂ = 180° U₂ = +pE Work required to rotate slowly is W = U₂ - U₁ = 2pE = 2(6.0×10⁻⁶)(1.5×10³) = 18×10⁻³ J = 18 mJ Final value: 18