For circuit 2, the power is
P_a2 = I_a2 V_a2

So if both the current and voltage halve,

P_a2 = (I_a1/2) (V_a1/2) = (1/4) I_a1 V_a1

P_a2 = (1/4) P_a1

P_a2 / P_a1 = 1/4

So the power is quartered since both the current and voltage are halved. It's no wonder that we have so much trouble seeing the bulbs glow.