A capacitor holds charge when disconnected from the supply because of the electric field created between its plates. When a capacitor is charged, electrons accumulate on one plate while the other plate loses electrons, creating a potential difference. The insulating dielectric material between the plates prevents these charges from recombining, so the stored energy remains in the electric field. Even after the external power source is removed, this electric field keeps the charges in place, allowing the capacitor to retain the charge for a significant period.
When a capacitor is disconnected from the power supply, it retains the charge that was stored in it. This happens because there is no conductive path for the charge to dissipate. The dielectric material between the capacitor plates prevents the charges from moving between the plates, effectively trapping them in place. Over time, due to imperfections and leakage currents through the dielectric, the capacitor might gradually lose its charge, but this process can take a long time, depending on the quality of the capacitor.
Charge stays on a capacitor because the dielectric material between the plates acts as an insulator, preventing the free flow of electrons between the plates. When a voltage is applied across the capacitor, an electric field is established, causing positive and negative charges to accumulate on opposite plates. Once the external voltage source is removed, this electric field continues to hold the charges in place, as there is no conductive path for them to move through. This property allows capacitors to store energy for later use.
The charge on a capacitor remains constant when the battery is disconnected because the circuit is incomplete, preventing any current flow. The separation of charges across the capacitor plates creates an electric field that maintains the stored charge. Without a path for electrons to travel, the charges cannot recombine, so the amount of charge remains unchanged. This stability is crucial for capacitors’ function in applications like temporary energy storage and filtering.
We do not supply charge to a capacitor continuously because capacitors are designed to store and release energy rather than consume it continuously. Once a capacitor reaches its maximum charge capacity (defined by its voltage rating), any additional charge would exceed its capacity, potentially leading to breakdown or damage of the dielectric material. Capacitors are typically charged to their required level and then used to provide a stable voltage or to smooth fluctuations in power supply, making continuous charging unnecessary and impractical.