The current I1 (in A) flowing through 1 Ω resistor in the following circuit is

Resistance in parallel=R1R2R1+R2=1(1)1+1=12Ω ⇒1/2Ω is in sereies with 2Ω ⇒Resistance in series= R'=12+2=52=2.5Ω ⇒2.5Ω is in parallel with 2Ω ⇒Resistance in parallel=R''=R1R2R1+R2=2(2.5)2+2.5=54.5=109Ω ⇒V=iR'' ⇒10=i109⇒i=9A Current through upper branch=I'=VR'=102.5=4A current through 1Ω=i'2=42=2A