4.183
U=cost =24v
Rtd=6+4+r2=10+r2
I=U/Rtd=24/(10+r2)
Pab =I^2.R=24^2/(10+r2)^2.(4+r2)
(10+r2)=x
max Pab<=>max [(x-6)/x^2]
y=(x-6)/x^2
x>0
y=1/x-6/x^2=1/24-[√6/x-1/(2√6)]^2
ymax <=>1/x=1/12<=>x=12<=>R2=2(om)
max Pab =24^2..ymax =24^2.1/24=24
Pmax=24w

mink hỏi bài 184 mà,..........

4.181
rd=2,5; ud=4,5
U=6
...
Id=Ud/rd=4,5/2,5=9/5=1,8(A)
Icn =im-Id=2-1,8=0,2(A)
Rcn =Ucn/icn=4,5/0,2=22,5(om)
Umc=6-4,5=1,5v
Rmc=1,5/2=0,75(om)
a)
MC/CN=Rmc/Rcn=0,75/22,5=1/30
b)
Rmn=Rmc+Rcn=22,5+0,75=30(om)
Rnc=4cm=> Rnc=24(om); Rcm=6(om)
Rtd=2,5.24/(2,5+24)+6=(12+31,8)/5,3
=43,8/5,3
I=U/Rtd=6.53/438=3.53/219~0,73(A)
den toi di
 

@ bai 184 ko nhin thay chi so R