COMEDK2024Evening ShiftPhysicsElectrostaticsActual
A neutral water molecule, modeled as an electric dipole with an effective charge equal to one elementary charge ( e = 1.6 10⁻¹⁹ C ), is placed in an electric field E = 2.5 10^4 NC ⁻¹ . The work done to rotate it by 180^ from its stable equilibrium position is 5 10⁻²⁵ J . Find the approximate separation of the centre of charges.
Options
- A0.625 10⁻⁹ ~m
- B0.625 10⁻¹⁰ ~m
- C1.25 10⁻¹⁰ ~m
- D0.998 10⁻¹⁰ ~m
Correct answer
B. 0.625 10⁻¹⁰ ~m
Step-by-step solution
Work done to rotate dipole by 180° from stable equilibrium: W = pE( 0° - 180°) = 2pE p = W 2E = 5 10⁻²⁵ 2 2.5 10^4 = 5 10⁻²⁵ 5 10^4 = 10⁻²⁹ C m p = qd d = p q = 10⁻²⁹ 1.6 10⁻¹⁹ = 0.625 10⁻¹⁰ m