1. The problem statement, all variables and given/known data Calculate the power absorbed at t=0,t=0+,and t=200 mS by each of the elements in the circuit of fig 11.25 if us is equal to (a) -10u(-t) V (b) 20 + 5u(-t) V 2. Relevant equations 3. The attempt at a solution http://www.chegg.com/homework-help/...pter-11-problem-3e-solution-9780073529578-exc The link posted above is the solution I'm trying to understand it I can also upload my work but it is more or less a copy of the solution so I saw no point. What I don't understand starting on the first part is how Vs(t)=-10u(-t) V=-10 at negative infinity to 0? First off what is u(-t) is this reactance or impedance? Furthermore if I took the limit if this as t approaches negative infinity would the function go to infinity not -10? So obviously it's not infinity even though it seems that it would, so I would have to assume u(-t)=1 for it to work. Why one because I am assuming that it has to do with current not flowing before time t=0? This also then begs another question as to why from 0 to infinity it is 0 implying that the voltage stops after time t=0 because u(-t)=0.Well anyways this is just two question of many that I have, so I am gonna ask this question first and slowly propagate through my errors in this problem?