1) d=10^-3 м I=2 A
j=I/S=I/(π*d²/4)=4*I/(π*d²)=4*2/(3.14*10^-6)=2.55*10^6 А/м²
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2) R=5 Ом L2=2*L1
R1=po*L1/S1
R2=po*L2/S2
V1=V2
S1*L1=S2*L2
S2=S1*L1/L2=S1/2
R2=po*2*L1/(S1/2)=4*R1=4*5=20 Ом
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6) U=5 B
R12=R1+R2=2+2=4 Ом
R34=R3*R4/(R3+R4)=2*2/(2+2)=1 Ом
Ro=R12+R34=4+1=5 Ом
Io=U/Ro=5/5=1 A
U1=U2=Io*R1=1*2=2 B (R1=R2)
I1=I2=Io=1 A
U3=U4=Io*R34=1*1=1 B
I3=I4=Io/2=0.5 A (R3=R4)
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