Chapter 26 79 Q26.16 The material of the dielectric may be able to support a larger electric field than air, without breaking down to pass a spark between the capacitor plates. Q26.17 The dielectric strength is a measure of the potential difference per unit length that a dielectric can withstand without having individual molecules ionized, leaving in its wake a conducting path from plate to plate. For example, dry air has a dielectric strength of about 3 MV/m. The dielectric constant in effect describes the contribution of the electric dipoles of the polar molecules in the dielectric to the electric field once aligned. Q26.18 In water, the oxygen atom and one hydrogen atom considered alone have an electric dipole moment that points from the hydrogen to the oxygen. The other O-H pair has its own dipole moment that points again toward the oxygen. Due to the geometry of the molecule, these dipole moments add to have a non-zero component along the axis of symmetry and pointing toward the oxygen. A non-polarized molecule could either have no intrinsic dipole moments, or have dipole
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