Question

A point charge causes an electric flux of -1.0 x 10³ Nm²/C to pass through a spherical Gaussian surface of 10.0 cm radius centered on the charge.
(a) If the radius of the Gaussian surface were doubled, how much flux would pass through the surface?
(b) What is the value of the point charge?

Answer 1

(a) If the radius of the gaussian surface is doubled, the electric flux through the new surface will still remain the same i.e. -1 x 10³Nm²C^-1 This is because the same charge is enclosed by the gaussian surface in the two cases.

(b) Φ = \(\frac{\mathrm{q}}{\varepsilon_{0}}\), q = \(\varepsilon_{0}\) Φ = 8.85 x 10^-12 x – 1 x 10³ = – 8.85 x 10^-9C