The driving force, shown as #4 is Torvald. He strives towards success and is primarily focused on how the world perceives him and although he seeks to better his family as well, he does so only by trying to improve his reputation.
The resistor (number 6) refers to Nora and shows one of the central themes in the play: Torvald's control over the various characters. This is most explicitly portrayed in his relationship with Nora, where he allows her certain powers or privileges, depending on their financial standing at the time. For example: He increases Nora's allowance when he gains his promotion or conversely, cuts off her power completely when he discovers the letter.
(number 7): Throughout most of the play, Nora acts as little more than an extension of Torvald's circuit; little more than a parasite (see the Bedford, 5th ed, 1528)where Nora comments that Torvald has "so much power now over all those people". After the incident with Krogstad's letter, she finally finds within herself the drive to become self-sufficient and in doing so severs ties with Torvald and becomes complete in herself, like a complete, independent circuit