When a DC source is suddenly disconnected from an RL circuit, it becomes source-free. Assuming the inductor has an initial current i0, the initial energy stored in the inductor can be determined. Applying Kirchhoff's voltage law around the loop and substituting the voltages across the inductor and resistor yields a first-order differential equation. Rearranging terms, integrating, and applying the limits gives a logarithmic equation. By taking exponential on both sides, the final expression of the circuit's natural response is determined. The current versus time graph shows an exponential decrease in the initial current. The current response can be expressed in terms of the time constant, which is the ratio of inductance to resistance. The current expression is used to determine the voltage and power dissipated across the resistor. Integration of dissipated power over time provides the expression for the energy absorbed by the resistor. As the time approaches infinity, the energy absorbed by the resistor approaches the initial energy stored in the inductor, implying that the initial energy is gradually dissipated in the resistor.