A neutral molecule is modelled as having an effective positive charge q=0.50e at a separation d=0.35 nm from an equal and opposite negative charge.

Sunday, 26 August 2018

1:07 AM

Machine generated alternative text: Question: A neutral molecule is modelled as having an ettective positive charge q = 0.50e at a separation d = 0.35 nm from an equal and opposite negative charge. part 1) What work is done by an electric field of 50 MVn1 1 to rotate this molecular dipole 1800 from parallel to antiparallel to the field? part 2) ay calculating the ratio, compare this with the thermal energy ( 21 kBT) associated with molecular rotation about one axis at a temperature of 300 K. rotation work/ thermal energy part 3) What surface charge density (ff = Q/A) is required on a parallel plate capacitor with no dielectric to produce a field ot 100 MV m ? Hint either use Gauss's law, or else write ü'0 different expressions for the capacitance. Check

 

Machine generated alternative text: Incorrect answer. Note: Your answers should be correct to 2 significant figures. Feedback tor Part 1) W = AU - A(-p • E) = - (-pE) = = 2qdE = Eed. Marks for this submissiom 0.00/0.33. This submission attracted a penalty of 0.11 Feedback tor Part 2) kBT 2Eed kill' • [The interesting thing is that they are comparable, and that fields ot 50 million volts/metre approach the breakdown field for many materials. So, to change substantially the orientation of small sized molecular dipoles requires very large fields.] Marks for this submissiom 0.00/0.33. This submission attracted a penalty of 0.11 Feedback tor Part 3) For a vacuum capacitor, . so A 8.9 x IF C d Marks for this submissiom 0.00/0.33. This submission attracted a penalty of 0.11 A correct answer 2.8e — 21, which can be typed in as follows: 2.8e-21 A correct answer is 1.4, which can be typed in as follows: A correct answer is 8.9e — 4, which can be typed in as follows: 8.ge-4

 

 

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