19) B

Maximum current is when there is minimum resistance. The lowest value of resistance = 10 + 2 = 12 Ω

I = V ÷ R = 6 ÷ 12 = 0.5 A

Minimum current is when there is maximum resistance. The highest value of resistance = 10 + 20 = 30 Ω

I = V/R = 6 ÷ 30 = 0.2 A

Difference = 0.5 – 0.2 = 0.30 A