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InterviewSolution
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The dipole moment of a water molecule is 6.3 × 10-30 Cm. A sample of water contains 1021 molecules, whose dipole moments are all oriented in an electric field of strength 2.5 × 105 N /C. Calculate the work to be done to rotate the dipoles from their initial orientation θ1 = 0 to one in which all the dipoles are perpendicular to the field, θ2 = 90°. |
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Answer» Data: p = 6.3 × 10-30 C∙m, N = 1021 molecules, E = 2.5 × 105 N/C, θ0 = θ1 = 0°, θ = θ2 = 90° W = pE(cos θ0 – cos θ) The total work required to orient N dipoles is W = NpE(cos θ1 – cos θ2) =(1021)(6.3 × 10-30)(2.5 × 105) = 15.75 × 10-4 J = 1.575 mJ |
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