Fisica, problema sui circuiti elettrici

Rp12 = R1//R2 = 40*20/60 = 40/3 di ohm

Rp34 = R3//R4 = 10*20/30 = 20/3 do ohm

Rp56 = R5//R6 = 10*10/20 = 5,0 ohm

Rt = Rp1+Rp2+Rp3 = (40+20+15)/3 = 75/3 = 25,0 ohm

I = V/Rt = 30/25 = 6/5 = 1,20 A 

I1 = I*R2/(R1+R2) = 1,2*20/60 = 0,40A ; P1 = 40*0,4^2 = 6,40 watt

I2 = I*R1/(R1+R2) = 1,2*40/60 = 0,80A ; P1 = 20*0,8^2 = 12,80 watt

V12 = V*Rp12/Rt = 30*40/(3*25) = 400/25 = 16,0 V 

I3 = I*R4/(R3+R4) = 1,2*20/30 = 0,8A ; P3 = 10*0,8^2 = 6,40 watt

I4 = I*R3/(R3+R4) = 1,2*10/30 = 0,40A ; P4 = 20*0,4^2 = 3,20 watt

V34 = V*Rp34/Rt = 30*20/(3*25) = 200/25 = 8,0 V 

I5 = I6 = I/2 = 1,2/2  = 0,6A ; P5 = P6 = 10*0,6^2 = 3,60 watt

V56 = V*Rp56/Rt = 30*5/25 = 30/5 = 6,0 V 

Rp1 =R1*R2/(R1+R2) = 40*20 /(40+20) = 800/60 = 40/3 ohm

Rp2 = R5*R6/(R5+R6) = 100/20 = 5 ohm

Rp3 = R3*R4/(R3+R4) = 20*10/(20+10) = 200/30 = 20/3 ohm

Req = Rp1+Rp2+Rp3 = 60/3 + 5 = 25 ohm

i = E/Req = 30/25 = 1.2 A

a)

i1 = Vp1 /R1 = Vab/R1 = (1.2*40/3)/40 = 0.4 A = 400mA   ---> Vab = 16V

i2 = Vab/R2 = 16/20 = 0.8 A = 800 mA

i5=i6=i/2 = 0.6 A = 600mA

i3 = Vp3/R3 = Vef / R3 = (1.2*20/3)/10 = 0.8 A      ---> Vef = 8V

i4 = Vef /R4 = 0.4 A   = 400 mA

b)

Vab = 16V

Vcd = Vp2 = i*Rp2 = 6 V

Vef = 8V

verifica    E = Vab +Vcd +Vef = 30 V 

c)

P1 = R1*i1² = Vab*i1 = 16*0.4 = 6.4 W

P2 = Vab*i2 = 16*0.8 = 12.8 W

P3 = Vp3*i3 = Vef*i3 = 8*0.8 = 6.4 W

P4 = Vef*i4 = 8*0.4 = 3.2 W

P5 = P6 = Vcd*i5 = Vcd*i6 = 6*0.6 = 3.6 W