Why does the current gradually increase in an inductor?
As current starts to flows through the inductor, a magnetic field is created around the inductor.
This magnetic field’s change generates an electromotive force. Due to the disturbance of this electromotive force, the current gradually increases.
If there is no change in current (DC), there is no change in the magnetic field anymore. Therefore, the inductor passes the current well like a general conductor.
If an alternating current (AC) current flows through the inductor, the inductor continues to create electromotive force, disturbing the current flow.
Why can’t the current flow continuously in the capacitor (capacitor)?
Fundamentally, a capacitor is a part of the wire broken.
Consider the case of switching on a circuit with a capacitor connected to it. Current flows while the capacitor is charging. However, when the capacitor is fully charged, no more current can flow.
If an alternating current (AC) current flows through the capacitor, it keeps the current flowing while repeating charging and discharging.
Where are these properties applied?
Inductors pass low-frequency currents, and capacitors pass high-frequency currents well.
Using this frequency characteristic, the inductor and capacitor can filter the electrical signal of the desired frequency. It is handy, such as wireless communication (for example, finding a TV or radio channel).