Question

Mach chon sog cua 1 may thu vo tuyen dien gom cuon day thuan cam L=2.10^-5H va 1 tu xoay co dien dug bien thien tu C1=10pF den C2 =500pF khi goc xoay bthien tu 0 den 180 do. Khi goc xoay cua tu bag 90 thi mach thu sog dtu co bc sog la:
A:26,64

B:188,4

C:134,54

D:107,52

Answer 1

Khi tụ xoay từ \(0^0 \rightarrow 180 ^0 : \) \(C_1 = 10pF \rightarrow C_2 = 500 pF\)

=> Tụ xoay từ \(0^0 \rightarrow 90^0: \) \(C_1 = 10pF \rightarrow C_x\)

Khi đó ta có: \((180-0) .(C_x-C_1) = (C_2-C_1).(90-0)\)

=> \(C_x-C_1 = \frac{(C_2-C_1)90}{180} = 245pF.\)

=> \(C_x = 255pF.\)

\(\lambda = c.2\pi \sqrt{LC} \approx 134,6m.\)

Chọn đáp án.C