Practice question

**Electric field** defined as E = F/q₀, force per unit positive test charge, unit N/C or V/m, direction along force on positive test charge. For point charge, E = k q/r² radially outward for q>0. Field lines start on positive and end on negative, density indicates strength. Outside shell: E = (k q/r²) . E = 9 × 10⁹ × (20 × 10⁻⁶/(0.35)²) = 9 × 10⁹ × (20 × 10⁻⁶/0.1225) = 1.469 × 10⁶ N/C . Substituting values gives 1.47 × 10⁶ N/C, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.