- #1

- 128

- 1

## Homework Statement

A solid ball of radius r1 has a uniform charge density ρ.

a) What is the magnitude of the electric field E(r) at a distance r>r1 from the center of the ball?

b) What is the magnitude of the electric field E(r) at a distance r<r1 from the center of the ball?

Express your answers in terms of ρ, r1, r, and ε.

## The Attempt at a Solution

a) i was thinking since the question asks to evaluate the electric field from outside the ball you can treat it as a point charge, E=Q/(4∏ε)r^2, and since the question states it wants the answer in terms of ρ, i used the formula ρ=Q/V and changed the Q to Vρ. after plugging in the equation for V → (4/3)∏r^3, things cancel and your left with E=(1/3)ρr/ε , but that is wrong.

i also tried this problem from the starting equation ∫EdA=Q/ε and got the exact same answer of E=(1/3)ρr/ε