L L R3 R R R4 R R=R3+R4R1R2→zs →=i(0)ex R1+R2 R eq R R +r iL(oet and e + r  t L L eq eq i i e R L R R R R R R R − → = → = + = + + (0) 1 2 1 2 3 4   t L t L i ( )e R R R i ( )e and i R R R i − − + = − + = − 0 0 1 2 1 2 1 2 2 1