Concepts Of Physics MCQ Edition [Volume 2]PhysicsGauss's Law
A uniformly distributed charge of density is contained within a long cylindrical volume. Determine the electric field at a point P located inside the cylindrical volume at a distance x from its axis, as shown in the figure.
Options
- A2 ₀ x
- Bx 2 ₀
- C₀ x
- Dx ₀
Correct answer
B. x 2 ₀
Step-by-step solution
Consider a coaxial cylindrical Gaussian surface of radius x and length L passing through point P . By Gauss's law, the total electric flux through this surface is: E d A = q_ enclosed ₀ Due to the symmetry of the long cylinder, the electric field E is radial and its magnitude is constant over the curved surface of the Gaussian cylinder. The flux through the flat circular ends is zero since the electric field is parallel to them. E(2 x L) = q_ enclosed ₀ The charge enclosed within the Gaussian surface is: q_ enclose