Electricity and Magnetism

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Change in Potential Energy in Flipping an Electric Dipole


Figure 1A depicts an electric dipole arranged so that its dipole moment is antiparallel to an applied electric field. Figure 1B show the same dipole, now rotated so that its dipole moment is parallel to the applied electric field.

Figure 1A and 1B

Timothy Black. Created for Albert.io. Copyright 2016. All rights reserved.

The magnitude of each of the two point charges is $q = 416 \text{ mC}$, and the charges are separated by a distance $d = 31.6 \text{ mm}$ from one another. The applied electric field is $\vec{E} = -914 \hat{y} \ \rm{\text{N}/\text{C}}$.

What is the change in potential energy in oscillating this dipole from the position of Figure 1A to the position of Figure 1B?


$\Delta U = -24.0 \text{ J}$


$\Delta U = 12.0 \text{ J}$


$\Delta U = 24.0 \text{ J}$


$\Delta U = -12.0 \text{ J}$