Question

Buna ma puteti ajuta va rog mult la problemele 27 si 29,le am pentru un test si am nevoie urgenta de rezolvare,mersii

Answer 1

27)Se da:
r=0,4ohm
R1=12ohm
R2=4ohm
R3=8ohm
R4=5,6ohm
I1=1A
a)R=?ohm
b)I=?ohm
c)U2=?V
d)Isc=?A

Rezolvare:
a)R=R123+R4

1/R123=(1/R1)+(1/R23)
1/R123=(1/R1)+(1/(R2+R3))
1/R123=(R1+R2+R3)/(R1*R2+R1*R3)
R123=(R1*R2+R1*R3)/(R1+R2+R3)

R=(R1*R2+R1*R3)/(R1+R2+R3)+R4
R=(12*4+12*8)/(12+4+8)+5,6=11,6ohm

b)I=I4=I123
I123=U123/R123

R123=(R1*R2+R1*R3)/(R1+R2+R3) (din a))

U123=U1=U23
U1=R1*I1⇒U123=R1*I1,at

I=R1*I1/[(R1*R2+R1*R3)/(R1+R2+R3)]
I=12*1/[(12*4+12*8)/(12+4+8)]=2A

c)I2=I3=I23

I2=U2/R2

I23=U23/R23
U23=U1
U23=I1*R1
R23=R2+R3⇒I23=I1*R1/(R2+R3), dar d-ce I23=I2,at

I1*R1/(R2+R3)=I2
I1*R1/(R2+R3)=U2/R2
U2=I1*R1*R2/(R2+R3)
U2=1*12*4/(4+8)=4V

d)Isc=E/r

I=E/(R+r)⇒E=I(R+r),at Isc=I(R+r)/r
R luam din puncul a), iar I din puncul b)
Isc=2*(11,6+0,4)/0,4=60A

29)Se da:
E=120V
r=2ohm
R1=6ohm
R2=2ohm
R3=4ohm
R4=6ohm
a)R=?ohm
b)I=?A
c)U2=?V
d)???, imi scrii ce ii scris la d) si adaug rezolvarea

Rezolvare:
a)E mai usor ca precedentul, aici toate is in paralel,
1/R=(1/R23)+(1/R1)+(1/R4)
1/R=(1/(R2+R3))+(1/R1)+(1/R4)
1/R=(R1+R2+R3)/(R1*R2+R1*R3)+(1/R4)
1/R=(R1*R4+R2*R4+R3*R4+R1*R2+R1*R3)/(R1*R2*R4+R1*R3*R4)
R=(R1*R2*R4+R1*R3*R4)/(R1*R4+R2*R4+R3*R4+R1*R2+R1*R3)

R=(6*2*6+6*4*6)/(6*6+2*6+4*6+6*2+6*4)=2ohm

b)I=E/(R+r)
I=120/(2+2)=30A

c)I2=I3=I23, I2=U2/R2⇒U2=R2*I2

U23=U1=U4=U
U=I*R⇒U23=I*R⇒I23=I*R/R23=I*R/(R2+R3)⇒I2=I*R/(R2+R3)⇒
⇒U2=I*R*R2/(R2+R3)

U2=30*2*2/(2+4)=20V