A first voltage variable material ("VVM") includes an insulative binder, first conductive particles with a core and a shell held in the insulating binder and second conductive particles without a shell held in the insulating binder; a second VVM includes an insulating binder, first conductive particles with a core and a shell held in the insulating binder, second conductive particles without a shell held in the insulating binder, and semiconductive particles with a core and a shell held in the insulating binder; a third VVM includes only first conductive particles with a core and a shell held in the insulating binder.