Question

The electric charges are distributed in a small volume. The flux of the electric field through a spherical surface of radius $10cm$ surrounding the total charge is $20Vm$. The flux over a concentric sphere of radius $20cm$ will be

• A. $20V.m$
• B. $25V.m$
• C. $40V.m$
• D. $200V.m$

Answer 1

Answer: (A)

$20V.m$

According to Gauss's law total flux coming out of a closed surface enclosing charge qq is given by
ϕ=∮E .dS =qε0ϕ=∮E→.dS→=qε0
From this expression, it is clear the total flux linked with a closed surface only depends on the enclosed charge and independent of the shape and size of the surface.
ϕ=∮E .dS =qε0=20Vmϕ=∮E→.dS→=qε0=20Vm
this qε0qε0 is constant as long as the enclosed charge is constant
The flux over a concentric sphere of radius 20cm=20Vm