A spherical volume contains a uniformaly distributed charge of density `2.0 xx 10^(4) C m^(3)`. Find the electric field at a piont inside the volume at a distance 4.0 cm from the centre.

Explanation

Given: V = volume charge density
` = 2.0 xx (10^-4) c/(m^3)`
` In order to find the electric field at a point`
` 4 cm = 4 xx (10^-2) m from the centre.`
Let us assume a concentric spherical
surface inside the sphere.
Now, `E xx ds = (q/ epsilon_0)`
But `q = r xx 4/3 pi (r^3)`
So, `E= ( q/ (epsilon_0).ds) `
= (2 xx (10^-4) xx 4 pi (r^3) / (epsilon_0). 3 . 4 pi(r^2))`
= 2 xx (10^-4) xx r / (3 epsilon_0) `
` = 21.12/7 xx (10^5)N/C `
` = 3.0 xx (10^5) N/C. `