In: Physics
A solid sphere of radius 40.0 cm has a total positive charge of 44.4
If charge is distributed uniformly in a sphere, then for finding
electric field at or outside the surface, it can be assumed that
the whole charge is concentrated at the centre of the sphere.
For finding electric field at a point inside the sphere, we should
assume a second sphere, which is concentring with the first and
goes through that point. We should ignore the charge outside the
second sphere because electric field because of that charge is 0.
We should consider only the charge within the second sphere.
According to Coulomb's law, the electric field at a distance r
meter from a point charge q coulomb is
9 * 10^9 * q/r^2 N/C
a) 0 cm from the center means at the center. The charge is uniformly distributed. Therefore, the electric field at the center = 0.
b) Volume within sphere of radius 10.0 cm = 4/3 * pi * (10
cm)^3
Volume of the complete sphere = 4/3 * pi * (40 cm)^3
Charge per unit volume = 44.4/[4/3 * pi * (40 cm)^3]