bai kho ve cuc tri mach RLC

0

0xalic

DK để UL max theo w là :

[TEX]w=\sqrt[2]{\frac{2}{2LC - R^2 . C^2}}[/TEX]

Biet f1 => w1

f2 => w2

Ta có UL1 = UL2

[TEX]\Leftrightarrow \frac{ZL1}{\sqrt[2]{R^2 + (ZL1 - ZC1)^2}}=\frac{ZL2}{\sqrt[2]{R^2 + ( ZL2 - ZC2)^2}}[/TEX]

[TEX]\Leftrightarrow (w2)^2 .( R^2 + ( ZL1 - ZC1 )^2)= (w1)^2 .( R^2 + ( ZL2 - ZC2 )^2)[/TEX]

[TEX]\Leftrightarrow R^2 .((w2)^2 -(w1)^2) - 2.\frac{L}{C}.((w2)^2 -(w1)^2) + \frac{1}{C^2}.(\frac{(w2)^4 - (w1)^4}{(w1)^2 .(w2)^2}) =0[/TEX]

[TEX]\Leftrightarrow 2LC - R^2 .C^2 = \frac{(w1)^2 + (w2)^2}{(w1)^2 .(w2)^2}[/TEX]

[TEX]\Rightarrow w= \sqrt[2]{\frac{2.(w1)^2 .(w2)^2}{(w1)^2 +(w2)^2}}[/TEX]

thay số vào dc kết quả hoi lẻ f = 74.67 Hz :(
 
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