Two rules, called Kirchhoff’s rules,
are very useful for analysis of electric circuits Given a circuit, we start by labelling currents in each resistor by a
symbol, say I, and a directed arrow to indicate that a current I flows
along the resistor in the direction indicated If ultimately I is determined
to be positive, the actual current in the resistor is in the direction of the
arrow If I turns out to be negative, the current actually flows in a direction
opposite to the arrow