ideal vs real capacitor
an ideal capacitor behaves as shown in your elementary text.
a real capacitor behaves differently. The dielectric:
air, plastic film, paper, or paper impregnated with an electrolyte (a polarized electrolytic) each behave differently when discharged.
The most amazing phenomena can happen with electrolytic capacitors:
1. The electrolytic capacitor can be charge say to +5v through a 1meg resistor.
A DVM is used to measure Vc =+5v, the voltage across the capacitor
2. The 1meg resistor is disconnected from the battery or power supply.
DVM: Vc =+5v
3. place a jumper wire across the electrolytic for say 15 sec.
DVM: Vc =0v
4. Disconnect the short circuit caused by the jumper wire.
the DVM will slowly indicate that Vc is charging from 0v back towards +5v , even though the battery is NOT connected!
This phenomena will not repeat with most dielectrics.
To be fair to use 1uf capacitor when comparing dielectrics.
The explanation has to do with the structure of the dielectric. An electrolytic dielectric flexes and moves while being charged.
The capacitor stored energy is NOT completely depleted by the short circuit.
In fact the electrolytic dielectric will restore itself to its uncharged state.
Only then will the stored energy be released, causing
it to be recharged from 0v towards +5v.
Most other dielectrics will behave similarly, but will cause much, much less recharge voltages say. +0.05 mv to 5 mv
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