Elettrostatica - fisica 2, appunti tratti dal corso prof. Minzioni, unipv Bioingegneria

Principio di conservazione della carica

F_elettrica = K · Q₁Q₂ / d²

Attrattiva se Q₁Q₂ < 0. Repulsiva se Q₁Q₂ > 0.

Es: F_a→q = K · Q_aq n̂₁ / |l₁|²

K = 1 / 4πε₀

ε₀ = 8.854 · 10^-12 C² / Nm²

Es: F_tot = Q₁q n̂₁ / 4πε₀d₁² + Q₂q n̂₂ / 4πε₀d₂²

Campo elettrico (prodotto di una carica puntiforme)

E̅ = F_tot / q

E̅(p) = 1 / 4πε₀ (Q₁ n̂₁ / |l₁|² + Q₂ n̂₂ / |l₂|²)

Forza di attrazione tra cariche elettriche

Attrattiva → Qq < 0. (Le due cariche hanno segno discordo)

Repulsiva se Qq > 0. (Le due cariche hanno segno concordo)

Es: Q --- n --- → q

F_{a □ q}F = K Q₁Q₂ n_u / | r₁₂ |²

9 * 10⁹ N*m² / C²

F _{a ➞ q} = 1/(4πε₀) Qq / |n|² n_u

Es: Q₁ --- n₁ ---Q₂ --- ... --- Q

F_tot = (Q₁q / |π_i|² Ω_i + Q₂q / |π₃|² π₄)

Unità di misura e calcolo

Unità di misura campo elettrico: Forza/Carica = N/C

Supponiamo di avere una lastra di ferro e valga misurare la carica immersa in un già posto ad 1mm dalla lastra.

--------------------------------------|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              &