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- PHY102 Physics II © Dr.Cem Özdoğan
- 23-8 Applying Gauss’Law: Planar Symmetry
- Figure 23-16a shows a cross section of a thin, infinite conducting plate with excess positive charge.
- The plate is thin and very large, and all the excess charge is on the two large faces of the plate.
- It will spread out on the two faces with a uniform surface charge density of magnitude 1.
- Just outside the plate this charge sets up an electric field of magnitude E = 1 /0.
- Figure 23-16b shows an identical plate with excess negative charge having the same magnitude of surface charge density 1.
- Now the electric field is directed toward the plate.
- If we arrange for the plates to be close to each other and parallel (Fig. 23-16c), the excess charge on one plate attracts the excess charge on the other plate, and all the excess charge moves onto the inner faces of the plates as in Fig. 23-16c.
- The new surface charge density, , on each inner face is twice 1.
- Thus, the electric field at any point between the plates has the magnitude: