Concepts Of Physics MCQ Edition [Volume 2]PhysicsGauss's Law
A nonconducting sheet with a large surface area and a thickness d contains a uniform charge distribution of density ho . Determine the electric field at a point P located inside the plate, at a distance x from the central plane, and identify the qualitative shape of the graph of E against x for 0 < x < d .
Options
- Ax 2 ₀ ; linearly increasing for 0 < x < d 2 , then constant for d 2 x < d
- Bx ₀ ; linearly increasing for 0 < x < d 2 , then constant for d 2 x < d
- Cx 2 ₀ ; linearly increasing for the entire range 0 < x < d
- Dx ₀ ; linearly increasing for the entire range 0 < x < d
Correct answer
B. x ₀ ; linearly increasing for 0 < x < d 2 , then constant for d 2 x < d
Step-by-step solution
Consider a Gaussian pillbox symmetric about the central plane of the sheet, with cross-sectional area A and extending to a distance x on both sides. For a point inside the sheet ( 0 The charge enclosed by the Gaussian surface is q_ enclosed = (2xA) . Using Gauss's law, E d A = q_ enclosed ₀ E(2A) = (2xA) ₀ E = x ₀ Thus, the electric field increases linearly with x for 0 For a point outside the sheet ( x d 2 ): The total charge enclosed by the Gaussian surface is q_ enclosed = (dA) . Using Gauss's law, E(2A) = (dA)