10.2.7—Kirchhoff’s laws to solve simple circuit problems

Assign unknown currents, use ΣI=0 at junctions and ΣV=0 around loops, then solve the simultaneous equations.

Choose current directions and loop orientations consistently; include source internal resistance and resistor drops where relevant.

A two-loop circuit can be solved by one junction equation plus one loop equation per independent loop.

A negative current is not a failed circuit—it means the chosen arrow was opposite to the physical current.