(a) When two resistors are connected in series, their resultant resistance is given by
R = R1+ R2
Here, R1=6 ,
R2=2
Therefore
The resulatant resistance, R = 6 + 2 = 8 Ω
(b) The current flowing through circuit is:
V = IR
I = V/R = 4/8
I = 0.5 A
(c) The p.d. across the 6 Ω resistor is:
V = 0.5 A x 6 Ω = 3 V