This kind of insulator can become a conductor if an external voltage is applied across the material.

The image can be 'erased' by resupplying the external voltage to the mesh restoring its constant potential.

But the gaps can be overcome by applying an external voltage, which helps the electrons to jump the gap, allowing current to flow.

Under the influence of an external voltage, both the electron and the hole can move across the material.

Also, ballistic transport has nothing to do with the presence of lack of an external voltage.

All materials need some kind of electric field across it (supplied by an external voltage or other means) to drive a net current flow.

Otherwise, a tunable external voltage can be added to one of the inputs in order to balance out the offset effect.

This reaction can occur through the application of an external voltage or through the release of chemical energy.

The electrolysis starts with the application of an external voltage between the electrodes.

Some dielectrics can generate a potential difference when subjected to mechanical stress, or change physical shape if an external voltage is applied across the material.