85-2 The source-free RL circuit i(t)--time var ying current R UR( L)ULO at t=0, i(t) KVL: VR+V,=0 or i+l-=0 dt di R di R R +--dt=0 or di t→ dt R In i(t)-Inl=--t .i(t=le l L§5-2 The source-free RL circuit 0 0 0 0 0 I i( ) I t at t , i(t ) i(t ) time var ying current = = = = − − t L R t i t I e L R i t I − − 0 = −  = 0 ln ( ) ln ( ) : + = 0 + = 0 dt di KVL vR vL or Ri L   + = = −  = − i( t ) t I dt L R i di dt L R i di dt or L R i di 0 0 0 (t)  L + − (t)  R − + R i(t) L