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JEE Main20208 Jan 2020Morning ShiftPhysicsElectrostaticsActual

In finding the electric field using Gauss law the formula E → = q e n c ε 0 A is applicable. In the formula ε 0 is permittivity of free space, A is the area of Gaussian surface and q e n c is charge enclosed by the Gaussian surface. This equation can be used in which of the following situation?

Options

  1. AOnly when the Gaussian surface is an equipotential surface
  2. BOnly when the Gaussian surface is an equipotential surface and E → is constant on the surface.
  3. COnly when E → = constant on the surface.
  4. DFor any choice of Gaussian surface.

Correct answer

B. Only when the Gaussian surface is an equipotential surface and E → is constant on the surface.

Step-by-step solution

According to Gauss law of electrostatics, the electric flux through an enclosed surface is given by ϕ E = q enc ε 0 From the formula of electric flux, ϕ = E → · d s → Also, the relation between electric field and electric potential is given by V = E → · d r → So, the formula E → = q enc ε 0 A is only applicable when the Gaussian surface is an equipotential surface and E → is constant on the surface.

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