In his pseudo science best seller "Chariots of the Gods" Eric Von Daniken conjectures that the Arc of the Covenant was a giant capacitor. It had an inner and outer layer gold plate with wood in between acting as a dielectric. The capacitor would pick up charge from the air (big capacitors charge themselves if the terminals are left unshorted). Discharge would explain the fireworks associated in the Bible with the Arc.
Exodus 25:10 Moses gives exact instructions from God how to build it.
Exodus 25:40 Make it exactly as God said.
2 Samuel 6:2 While moving the arc Uzzah touches it and is dropped dead as if struck by lightning.