When a capacitor is charging, what happens to the current flow?

When a capacitor is charging, the current flow decreases over time. This behavior can be understood through the principles of capacitance and the nature of the charging process.

Initially, when a voltage is applied across the capacitor, the current is at its maximum because the capacitor acts almost like a short circuit, allowing a large amount of current to flow as it begins to accumulate charge. As the capacitor charges, the voltage across its plates rises, and thus the potential difference between the voltage source and the capacitor decreases. This reduction in the potential difference results in a decrease in the current flow.

Eventually, as the capacitor becomes fully charged, the current will approach zero since the voltage across the capacitor equals the voltage of the power source.

This gradual decrease in current is characteristic of an RC (resistor-capacitor) charging circuit, where the time constant defined is the product of the resistance and capacitance (τ = R × C). This time constant indicates how quickly the capacitor charges — more specifically, it defines the rate at which the current decreases. Thus, it is accurate to say that as time progresses during the charging phase, the current diminishes until it effectively halts once the capacitor is fully charged.