Question

Two solid spheres, both of radius $5cm$, carry identical total charges of $2\mu C$. Sphere $A$ is a good conductor.Sphere $B$ is an insulator, and its charge is distributed uniformly throughout its volume.
How do the magnitudes of the electric fields they separately create at radius 4 cm compare?

• A. $E_A>E_B=0$
• B. $E_A>E_B>0$
• C. $E_A=E_B>0$
• D. $0$
• E. $0=E_A<E_B$

Answer 1

Answer: (E)

$0=E_A<E_B$

The field within the conductor is zero. The field a distance $r$ from the center of the insulator is proportional to $r$, so it is $4/5$ of its value at the surface.