Passive sign convention

The passive sign convention is a broad rule we use in circuit analysis to keep our calculations and assumptions consistent. Some of the core ideas are:

• When an element is:
  • Absorbing energy, power is positive $p(t)>0$
  • Delivering energy, power is negative $p(t)<0$
• We track the polarity of voltage across an element by marking one terminal as the positive and one as the negative. This determines the reference polarity.
  • How do you determine the marks? It’s arbitrary, but must remain fixed after we decide, during our analysis.
• The reference direction for current in an element is from the positive to negative terminal.
  • i.e., it’s determined by the reference polarity for voltage.