DC circuits involve three fundamental elements: resistance, inductance, and capacitance. Resistance opposes the flow of current or electrons in a conductor and is measured in ohms (Ω), with Ohm's Law defining it as V = IR. Inductance resists changes to the magnitude or direction of current within a material; its unit is henry (H) with formulas like V = L(dI/dt). Capacitance stores electric charge within materials, measured in farads (F), using equations such as I = C(dV/dt). Each element has unique phasor diagrams illustrating their voltage-current relationships.