- generally theyre aluminum electrolytic capacitors, the layer of insulating aluminum oxide on the surface of the aluminum plate acts as the dielectric
- the thinness of this layer allows for a relatively high capacitance in a small volume...this can withstand an electric field strength of the order of 109 volts per meter
- high capacitance and high voltage result in high energy density
- capacitors are polarized, positive and negative
- they may catastrophically fail if voltage is reversed...a reverse-bias voltage above 1-1.5 V destroys the center layer of dielectric material via electrochemical reduction (redox reactions)-short circuiting it, the electrolyte rapidly heats up and leaks or bursts...oxygen gas...BOOM
- run too much voltage through them this will happen too...capacitors are safety rated eg. 15v, 18v, 20v etc.... run 18v through a capacitor rated at 15V...BOOM
- the explosion will depend on the charge...if the cap shorts out it discharges through a very low resistance in a very short time...a fully charged capacitor can vaporize a screwdriver...a partial charge has less spectacular results...no charge, no BOOM
- so dont short them and dont overload them