For a concentric-shell system, the electric flux through a centred Gaussian sphere is:
+2×10⁶ V·m for 0<r< $r_A,$
-5×10⁶ V·m for $r_A<r<r_B,$
+5×10⁶ V·m for r> $r_B.$
For which finite interval of r is the electric field identically zero?

Question

For a concentric-shell system, the electric flux through a centred Gaussian sphere is:

+2×10⁶ V·m for 0<r< $r_A,$
-5×10⁶ V·m for $r_A<r<r_B,$
+5×10⁶ V·m for r> $r_B.$

For which finite interval of r is the electric field identically zero?

Options

G1 Physics · Accepted Answer

For a centred Gaussian sphere, E(4πr²) = Φ, so E = Φ/(4πr²). Since Φ is nonzero in every finite interval, there is no finite interval where E=0.