Объяснение:

1. А, В

2. R1,2 = R1 × R2/(R1 + R2) = 10 × 15/(10 + 15) = 6 (Ω)

R = R1,2 + R3 = 26 (Ω)

3. R = R1 + R2 = 6 + 3 = 9 (Ω)

I = V/R = 4.5/9 = 0.5 (A)

5. 1. Б; 2. А; 3. Г; 4. В

6. R1 = 8 Ом

R2 = 12 Ом

R = R1 × R2/(R1 + R2) = 4.8 (Ω)

I1 ~ 1/R1

I2 ~ 1/R2

R2 > R1, I1 > I2

7. R = R1 × R2/(R1 + R2) + R3 = 6/5 + 5 = 6.2 (Ω)