A charge q is placed at the centre of a sphere of radius r. The electric flux crossing the sphere is $\phi$. If both the charge and radius of the sphere are doubled, the electric flux crossing the sphere will be
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → $2\phi$
By Gauss’s law:
$\phi = \frac{q}{\epsilon_0}$
Flux depends only on the enclosed charge, not on the radius of the sphere.
If charge is doubled ($q \to 2q$) and radius is doubled ($r \to 2r$),
New flux $\phi' = \frac{2q}{\epsilon_0} = 2\phi$
Answer: The new electric flux is $2\phi$