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- PHY102 Physics II © Dr.Cem Özdoğan
- 23-8 Applying Gauss’Law: Planar Symmetry
- Figure 23-15 shows a portion of a thin, infinite, nonconducting sheet with a uniform (positive) surface charge density .
- We need to find the electric field E at a distance r in front of the sheet.
- A useful Gaussian surface is a closed cylinder with end caps of area A, arranged to pierce the sheet perpendicularly as shown.
- From symmetry, E must be perpendicular to the sheet and hence to the end caps.
- Since the charge is positive, E is directed away from the sheet.
- Because the field lines do not pierce the curved surface, there is no flux through this portion of the Gaussian surface.
- Here A is the charge enclosed by the Gaussian surface. Therefore,
- Compare with the solution at Chapter 22!!
- Thus E.dA is simply EdA, then the Gauss’s law:
- uniform charge distribution