CORRIGES : 

EXERCICE I :

1. R = R1 + R2 + R3 = 5 + 10 + 15 = 30 Ω 

2. I = U / R = 6 / 30 = 0,2 A

EXERCICE II :

U = R × I = 12 × 0,5 = 6 V

EXERCICE III : 1. R = 4 + 8 = 12 Ω 

2. I = U / R = 12 / 12 = 1 A 

3. U(R1) = R1 × I = 4 × 1 = 4 V 

   U(R2) = 8 × 1 = 8 V