Mọi người cùng thử sức nhé. Khó lém đấy !~~~~~~!

[proboyvip1995]

E1 = 6(v), r1 = 2(ôm), r2 = 1(ôm)
R1 = R2 = R3 = 3(ôm)
vôn kế chỉ 1,5(v), Rv >>>>

Tìm E2= ?

 

[proboyvip1995]

Giải:

TH1: U[SUB]CD[/SUB] = 1,5(v)
R[SUB]13 [/SUB]= 6 (ôm)
R[SUB]123[/SUB] = 2 (ôm)
U[SUB]CD [/SUB]= U[SUB]CA[/SUB] + U[SUB]AD[/SUB]
.//...= -U[SUB]AC[/SUB] + U[SUB]AD[/SUB] = -(E - I[SUB]1[/SUB]'.r[SUB]1[/SUB]) + I[SUB]1.[/SUB]R[SUB]1[/SUB] (1)
.......I[SUB]1[/SUB]' = I[SUB]1[/SUB] + I[SUB]2[/SUB]
(R[SUB]2[/SUB]//R[SUB]3[/SUB]) -> U[SUB]2[/SUB] = U[SUB]13[/SUB]
............<-> I[SUB]2.[/SUB]R[SUB]2[/SUB] = I[SUB]1.[/SUB]R[SUB]13[/SUB]
............<-> 3I[SUB]2[/SUB] + 6I[SUB]1[/SUB] -> I[SUB]2[/SUB] = 2I[SUB]1[/SUB] (2)
...-> I[SUB]1[/SUB]' = 3I[SUB]1[/SUB]
Từ (1) và (2) ta có:
.......U[SUB]CD[/SUB] = -(E - 3I[SUB]1.[/SUB]r[SUB]1[/SUB]) + I[SUB]1.[/SUB]r[SUB]1
[/SUB]<-> 1,5 = -6 + 9I[SUB]1[/SUB]
<-> I[SUB]1[/SUB] = 5/6 ~ 0,83 ~ 1 (ôm)
-> I[SUB]1[/SUB]' = 3 (ôm)
U[SUB]CD[/SUB] = U[SUB]CB[/SUB] + U[SUB]BD[/SUB]
.......= E2 - I[SUB]1[/SUB]'.r[SUB]2[/SUB] - I[SUB]3.[/SUB]R[SUB]3[/SUB]
-> E2 = 1,5 + 3 + 3 = 7,5(v)

Mình hết lực rùi........Các bạn làm giúp mình " TH2: U[SUB]DC [/SUB]= 1,5(v).........phù