1. What is the significance of the negative sign in the equation E- = -∇ V ?
2. State Gauss's law.
3. Can we use Gauss's law in each of the following cases: (a) ρv = kρ2, (b) ρv = kρ cos φ, (c) ρv = k/ρ and ρ /= 0, (d) ρv = kr , (e) ρv = kr cos θ , (f ) ρv = kr cos φ?