Final answer:
A capacitor charging circuit consists of a battery, an uncharged capacitor, and a resistor. The RC time constant, given by the product of the resistance and capacitance, represents the time it takes for the current to decrease to about 37% of its initial value.
Step-by-step explanation:
A capacitor charging circuit consists of a battery, an uncharged capacitor, and a resistor. When the circuit is closed, the capacitor starts to charge and the current decreases over time according to the RC time constant. The time constant, in seconds, is given by the product of the resistance and the capacitance in farads: RC = R * C. It represents the time it takes for the current to decrease to about 37% of its initial value.