When the cross does not reach the edges of the field, it becomes a mobile charge.

This leaves equal and opposite charges exposed on the other face, where there is a scarcity of mobile charges.

Insulators are non-conducting materials with few mobile charges and which support only insignificant electric currents.

Gases or liquids containing mobile electrical charges are subject to the influence of a magnetic field.

The mobile charges not only establish but also move in response to the associated Coulomb force, .

In a perfect dielectric there are no mobile charges but lots of bound charges, positive and negative.

The mobile charges in the wire are not the least concerned about the origin of the electric field.

The force on the mobile charges is still qE but now the charges may follow the electric field all the way around the ring.

The device does not attain its blocking capability until the mobile charge in the junction is depleted.

It is the electrostatic field of the charged object C which causes the mobile charges to move.