Section 33.7 Dielectrics Bootcamp
Subsection 33.7.1 Electric Dipoles
Problem 33.7.1. Polarization of Carbon Atom in External Electric Field.
Follow the link: Checkpoint 33.1.5.
Problem 33.7.2. Induced Dipole Moment in Sodium Atom.
Follow the link: Checkpoint 33.1.6.
Problem 33.7.3. Polarization of Water Molecule and Charges on Each Atom.
Follow the link: Checkpoint 33.1.7.
Subsection 33.7.2 Force and Torque on Electric Dipoles
Problem 33.7.4. (Calculus) Force and Torque on a Dipole in a Non-uniform Field.
Follow the link: Checkpoint 33.2.3.
Problem 33.7.5. (Calculus) Computing Force on a Dipole by a Point Charge.
Follow the link: Checkpoint 33.2.4.
Subsection 33.7.3 Potential Energy of Electric Dipoles in an External Field
Problem 33.7.6. Energy for Flipping a Dipole Upside Down.
Follow the link: Checkpoint 33.3.2.
Problem 33.7.7. Electrostatic Energy of a Dipole in the Presence of a Point Charge.
Follow the link: Checkpoint 33.3.3.
Subsection 33.7.4 Electric Potential of a Dipole
Problem 33.7.8. Force Between an Electric Dipole and a Point Charge.
Follow the link: Checkpoint 33.4.3.
Problem 33.7.9. Force on a Point Charge from an Electric Dipole.
Follow the link: Checkpoint 33.4.4.
Problem 33.7.10. Torque on a Dipole from Field of another Electric Dipole.
Follow the link: Checkpoint 33.4.5.
Subsection 33.7.5 Linear Dielectrics
Problem 33.7.11. Electric Field in Paper Between Two Charged Paper Plates.
Follow the link: Checkpoint 33.5.4.
Problem 33.7.12. Polarization of Plastic Wrapped Around a Charge Steel Sphere.
Follow the link: Checkpoint 33.5.5.
Problem 33.7.13. Electric Field and Polarization of Two Different Layers of Dielectrics Filling Space Between Parallel Plates.
Follow the link: Checkpoint 33.5.6.
Subsection 33.7.6 Miscellaneous
Problem 33.7.14. Torque on Ammonia Molecule and Energy for Flipping the Orientation of Dipole Moment.
An ammonia molecule has an electric dipole moment of \(5.0 \times 10^{-30}\) C.m. It is placed in an external electric field of \(1,000\) V/m. (a) What is the torque on it at the time the dipole is pointed at a \(60^{\circ}\) angle with respect to the electric field? (b) Once aligned, how much energy will it take to flip the orientation of the dipole by \(180^{\circ}\text{?}\) Write your answer in the electron volt (eV) unit. The unit \(1\) eV = \(1.6\times 10^{-19}\) J.
Use definitions
(a) \(4.3\times 10^{-27}\) N.m, (b) \(6.3\times 10^{-8}\) eV.
(a) The torque on a dipole is equal to the vector product of the dipole moment and the electric field. Therefore, the magnitude of the torque will be
The direction of the torque vector can be obtained by using the right-hand rule. therefore, if you place the vector \(\vec p\) towards the positive \(x\)-axis and vector \(\vec E\) in the \(xy\)-plane towards a direction in the space \(y>0\text{,}\) then the torque will be pointed towards the positive \(z\)-axis.
(b) Flipping of a dipole's direction requires energy equal to \(2pE\text{.}\)