Choose the incorrect statement :
(a) The electric lines of force entering into a Gaussian surface provide negative flux.
(b) A charge 'q' is placed at the centre of a cube. The flux through all the faces will be the same.
(c) In a uniform electric field net flux through a closed Gaussian surface containing no net charge, is zero.
(d) When electric field is parallel to a Gaussian surface, it provides a finite non-zero flux.
Choose the most appropriate answer from the options given below
(a) The electric lines of force entering into a Gaussian surface provide negative flux.
(b) A charge 'q' is placed at the centre of a cube. The flux through all the faces will be the same.
(c) In a uniform electric field net flux through a closed Gaussian surface containing no net charge, is zero.
(d) When electric field is parallel to a Gaussian surface, it provides a finite non-zero flux.
Choose the most appropriate answer from the options given below
- (A)(c) and (d) only
- (B)(a) and (c) only
- (C)(d) only✓ Correct
- (D)(b) and (d) only
Answer: (C)
Solution
Flux is . Field lines entering a closed surface point opposite to the outward normal and give negative flux, so the statement that entering lines provide negative flux is correct. A charge at the centre of a cube sends equal flux through each of the six faces by symmetry, so the statement that the flux through every face is the same is correct. By Gauss's law the net flux through a closed surface enclosing no charge is zero whatever the uniform external field, so that statement is correct. When the field is parallel to a surface it is perpendicular to the area vector, so the flux through that surface is zero, not finite. The only incorrect statement is that a field parallel to a Gaussian surface provides a finite non-zero flux.
JEE Main · 2021 · 31 Aug 2021 · Shift 2 · Single correct option