Tutti i dati hanno due sole cifre significative.
* A ≡ P1(- 3, - 1) cm = (- 3/10^2, - 1/10^2) m; q1 = + 7/10^6 C
* B ≡ P2(+ 1, + 4) cm = (+ 1/10^2, + 4/10^2) m; q2 = - 4/10^6 C
* C ≡ P3(+ 1, + 3) cm = (+ 1/10^2, + 3/10^2) m; q3 = - 2/10^6 C
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Distanze
* |AC| = d1 = √2/25 ~= 0.057 m
* |BC| = d2 = 1/100 = 0.010 m
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Campo elettrico in P(x, y) della carica q in Q(u, v) a distanza d
* E(P) = (1/(4*π*ε))*q*(P - Q)/d^3
dove, per ε ~= ε0, si ha
* k = 1/(4*π*ε0) ~= 9.0 N·(m/C)^2 (con due sole cifre significative)
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Per (P = C(1/10^2, 3/10^2)) & (Q = A(- 3/10^2, - 1/10^2)) & (q = 7/10^6) si ha
* E1(C) = 9*(7/10^6)*((1/10^2, 3/10^2) - (- 3/10^2, - 1/10^2))/(√2/25)^3 =
= (63*√2/6400, 63*√2/6400) V/m
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Per (P = C(1/10^2, 3/10^2)) & (Q = B(1/10^2, 4/10^2)) & (q = - 4/10^6) si ha
* E2(C) = 9*(- 4/10^6)*((1/10^2, 3/10^2) - (1/10^2, 4/10^2))/(1/100)^3 =
= (0, 9/25) V/m
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* E(C) = E1(C) + E2(C) =
= (63*√2/6400, 63*√2/6400) + (0, 9/25) =
= (63*√2/6400, 9*(256 + 7*√2)/6400) V/m