# If a capacitor blocks DC then why is DC used to charge a capacitor ?

A capacitor blocks DC because it cannot sustain a continuous flow of direct current due to its inherent property of opposing a steady voltage. When a DC voltage is applied to a capacitor, it initially allows current to flow as it charges or discharges to equalize the voltage across its plates. However, once the capacitor reaches full charge (or discharge), it blocks any further flow of DC current. This occurs because the capacitor charges up to the applied DC voltage, and then the voltage across it stabilizes, resulting in zero current flow through the capacitor in a steady-state condition.

DC blocking capacitors, also known as coupling capacitors, are deliberately used in electronic circuits to prevent DC voltage from passing while allowing AC signals to pass through. This property is essential in applications where DC interference needs to be blocked, such as in audio amplifiers or radio frequency circuits, where only AC signals are desired for amplification or processing.

Capacitors block DC but allow AC because AC signals alternate in direction, causing the capacitor to continuously charge and discharge as the polarity changes. As a result, the capacitor permits the alternating current to pass through by alternately storing and releasing charge, thereby allowing the AC signal to propagate while blocking any steady DC component.

Charging a capacitor under a DC voltage source is a standard method to store electrical energy in the capacitor’s electric field. When a capacitor is connected to a DC voltage source, current flows into the capacitor until it reaches the voltage of the source. This process charges the capacitor with energy proportional to the voltage applied and the capacitance value. Once charged, the capacitor can store this energy until discharged or used in a circuit.

Yes, DC can charge a capacitor. When a DC voltage is applied across the terminals of a capacitor, the capacitor charges up until the voltage across its plates equals the applied DC voltage. The rate at which the capacitor charges depends on its capacitance and the resistance in the charging circuit (if present). After charging, the capacitor holds the electric charge until it is discharged or connected to a different circuit.

In summary, capacitors block DC because they cannot sustain a steady current flow under a constant voltage once they reach a steady-state condition. DC blocking capacitors are utilized in circuits to prevent DC interference while allowing AC signals to pass through, making them essential components in various electronic applications where AC signal processing is required. Charging a capacitor under a DC voltage source is a fundamental method to store electrical energy in capacitors, enabling them to perform various functions in electronic circuits.