Bai7: cho mach djen nhu hv biet:
U=100V;I1=2A;R1=20Ω;R2=2R3
Tinh:
a>Mach P1 nt RAB
I1=IAB=I=2(A);
Rtd=R1 RAB;
Rtd=U/I=100/2=50(Ω);
=>RAB=Rtd-R1=20(Ω);
RAB=(R2*R3/R2 R2)=30;
R2=2R3
b>IAB=2(A);
UAB=IAB*RAB=60(V)
c>P1=I1^2*R1=...(W);
P2=U2^2/R2=U^2AB/R2=...(W);
P3=U3^2/R3=U^2AB/R3=...(W)
Bai9:
cho R1=20om, R2=R3=10om, R4=6om,R5=R6=12om, U=220V
Tinh:
mach R1nt RAB nt R2
a) Rtd=R1 RAB R2;
RAB=R3 * (R456/R3 R456);
R456=R4 R56;
R5=//R6=12om;
R56=R5/2=6om;
=>R456=12om;
=>RAB=10*12/10 12 =5,5om;
=>Rtd=20 5,5 10
=35,5om
b) I1=IAB=I2=I=U'/Rtd =220/35,5=6,2(A);
I3=U3/R3=IAB*RAB/3 =6,2*5,5/10=3,4(A);
I4=I56=I456=UAB/R456=62*5,5/12=2,8(A);
R5//R6;
=>I5=I6=I4/2=2,8/2= 1,4(A)
c)P1=I1^2*R1=...(w)
Bai10:
R1=R2=R3=R4=60(om);
R3=120W
Tinh:
a) Vi R2//R3//R4(gt)
R1=R2=R4=2R3(gt)=60(öm);
1/RAB=1/R2 1/R3 1/R4=1/2R3 1/R3 1/2R3=(1 2 1)/2R3=2/R3;
=>RAB=R3/2=30/2=15(om);
ADCT: P=R.I^2=>I=|/"p/R
=>I3=|/"P3/R3=|/"120/30=2(A);
=>UAB=U3.R3=2.30=60(W);
vi R2=R4=>I2=I4=UAB/R2=60/60=1(A);
R2//R3//R4;
I=I2 I3 I4=1 2 1=4(A)
b) U=I.R=I(R1+RAB)= (60+15).4=300V
c) ADCT: P=R.I^2
=>p1=R1.I1^2=60.4^2=960(w);
p2=R2.I2^2=60.1^2=60(w)
