Question

Cine stie sa faca o problemă de clasa a X a la fizica? ;))❤

Answer 1

Răspuns:

E-I₁r = I₁R₁ = U₁ ⇒ I₁ = E/(r+R₁)

E-I₂r = I₂R₂ = U₂ ⇒ I₂ = E/(r+R₂)

P₁ = U₁I₁ = I₁²R₁ = R₁E²/(r+R₁)²

P₂ = U₂I₂ = I₂²R₂ = R₂E²/(r+R₂)²

a)

P₁=P₂ ⇒ R₁E²/(r+R₁)² = R₂E²/(r+R₂)²

⇔ R₁/(r+R₁)² = R₂/(r+R₂)²

⇔ √R₁/(r+R₁) = √R₂/(r+R₂)

⇒ (r+R₂)√R₁ = (r+R₁)√R₂

⇔ r√R₁+R₂√R₁ = r√R₂+R₁√R₂

⇒ r = (R₁√R₂-R₂√R₁)/(√R₁-√R₂)

r = (√R₁+√R₂)(R₁√R₂-R₂√R₁)/(R₁-R₂)

r = (R₁√R₂√R₁-R₂√R₁√R₁+R₁√R₂√R₂-R₂√R₁√R₂)/(R₁-R₂)

r = (R₁-R₂)√R₁√R₂/(R₁-R₂)

r = √R₁√R₂

b)

P = P₁ = R₁E²/(r+R₁)²

P = R₁E²/(√R₁√R₂+R₁)²

P = R₁E²/[√R₁(√R₂+√R₁)]²

P = R₁E²/R₁(√R₂+√R₁)²

P = E²/(√R₂+√R₁)²

⇒ E² = P(√R₁+√R₂)²

⇒ E = (√R₁+√R₂)√P