Question

Calculați raportul rezistentor electrice a doua fire confectionate din acelasi material , care au aceeasi lungime dar care au raportul diametrelor egal cu 3

Answer 1

Răspuns:

$\frac{d1}{d2}=3 /=> d1=3d2\\l1=l2\\p1=p2\\R1=p\frac{l}{S1} \\R2= p\frac{l}{S2} \\S1 = \frac{\pi d1^{2} }{4} \\S2 = \frac{\pi d2^{2} }{4}\\ \frac{R1}{R2}=\frac{p\frac{l}{S1} }{p\frac{l}{S2} } = \frac{\frac{\frac{1}{\pi d1^{2} } }{4} }{\frac{\frac{1}{\pi d2^{2} } }{4} } \\\frac{R1}{R2}= \frac{\frac{1}{\pi d1^{2} } }{\frac{1}{\pi d2^{2} } } \\ \frac{R1}{R2}=\frac{1}{d1^{2} } \frac{d2^{2} }{1} \\ \frac{R1}{R2}=\frac{1}{3d2^{2} } \frac{d2^{2} }{1} =\frac{1}{3}$