In a purely resistive DC circuit, how quickly does current reach its maximum value when energized?

In a purely resistive DC circuit, the current reaches its maximum value immediately when the circuit is energized. This is because the behavior of a resistive load is defined by Ohm's Law, where current (I) is equal to voltage (V) divided by resistance (R). When the voltage is applied, there is no time delay for the current to build up as there might be in circuits with inductive or capacitive components.

In the absence of these reactive components, the circuit's resistance determines how much current flows right from the moment the voltage source is connected. As a result, once the circuit is closed, the current stabilizes instantly at its maximum steady-state value dictated by the external voltage and the resistance of the circuit.

The other options represent scenarios that would apply to circuits with capacitive or inductive elements, where the buildup of current would not be instantaneous due to electrical storage and magnetic flux changes affecting the flow. In purely resistive circuits, such delays do not occur.