Question

Exercitiul 8 va rog frumos

Answer 1

Se da:
R1=200ohm
R3=400ohm
R=200ohm
U2=50V
a)I3=?A
b)t=10min=600s; Q=?J
c)P12=?W

Formule:
a)I3=U3/R3

U3=U12

U12=I12*R12

R12=R1+R2

1/R=(1/R12)+(1/R3)
1/(R1+R2)=(1/R)-(1/R3)
1/(R1+R2)=(R3-R)/(R*R3)
R1+R2=R*R3/(R3-R)
R2=[R*R3/(R3-R)]-R1
R2=[200*400/(400-200)]-200=200ohm

I12=I1=I2
I2=U2/R2
I12=U2/R2

I3=U12/R3
I3=I12*R12/R3
I3=U2*(R1+R2)/R2*R3
I3=50*(100+200)/400*300=0,125A

b)Q=L
Q=t*U²/R

U=U12=U3

U3=I3*R3

U=I3*R3
U²=(I3*R3)²

Q=t*(I3*R3)²/R
Q=600*(0,125*400)²/200=150J

c)P12=U12²/R12

U12=U3

U3=I3*R3

U12=I3*R3
U12²=(I3*R3)²

R12=R1+R2

P12=(I3*R3)²/(R1+R2)
P12=(0,125*400)²/(200+200)=6,25W