Circuit modeled: source V through series R1 reaches an internal node; R2 goes from that node to ground (forming a divider), and R3 continues from that node to output terminal A (ground = terminal B). Thevenin voltage V_th is the open-circuit voltage at A-B: since no current flows through R3 with the load removed, V_th = V×R2/(R1+R2). Thevenin resistance R_th is the resistance seen from A-B with the source zeroed (shorted): R_th = R3 + (R1∥R2). Norton equivalent: I_N = V_th/R_th, R_N = R_th — the two equivalents predict identical behavior for any load. With a load R_L entered, load current and voltage are computed directly from the equivalent (I = V_th/(R_th+R_L)) rather than re-solving the original network, demonstrating why the simplification is useful.