Capacitors lose charge over time, even when they are disconnected. Why does it happen?

Is there a way to keep the charge longer, like for years.

If you cover the plates with better insulator, will it reduce the charge loss?


That's because the material between the plate is a good, but not perfect insulator and it has a non-infinite resistance. Therefore it acts as a very high resistance across the terminals of the capacitor, leading to slow self-discharge.

Of course using better insulator materials could lead to lower self-discharge rate, as it is exploited in FLASH memory chips: in flash memory the bits are stored in tiny capacitors (formed by a floating gate inside a MOS structure) that can retain their charge for years.

Since self-discharge is due to dielectric resistance, you can improve it (i.e. make it bigger) by using a dielectric with higher resistivity and with higher thickness. Increasing the thickness of the dielectric between the plates means decreasing the capacitor capacitance, though. Moreover, also using a dielectric with better insulating properties can lead to a decrease in capacitance since some good insulating materials have poor dielectric constants (i.e. low relative permittivity).

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.