CBSE Class 12 · 2006 · ElectrostaticsShort Answer

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What is electric flux? Write its S.I. units. Using Gauss's theorem, deduce an expression for the electric field at a point due to a uniformly charged infinite plane sheet.

Solution

Electric flux is the number of field lines crossing a surface normally:

ϕ = E \cdot Δ S, S.I. unit N m^{2} C^{- 1}

Take a cylindrical pillbox of face area

A

piercing the sheet symmetrically; the field is normal and equal on both faces:

2 E A = \frac{σ A}{ε _{0}}

E = \frac{σ}{2 ε _{0}}

directed away from the sheet and independent of distance.

CBSE Class 12 Board · 2006 · Subjective

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