If the current consists of particles carrying negative charge, then the direction of the current is opposite the direction of the motion of the particles. Metals tend to be good conductors, while glass, plastic, and other non-metallic materials are usually insulators. All materials contain both positive and negative charges. In metals, negatively charged electrons can escape from atoms and are free to move about the material. When atoms lose one or more electrons, they become positively charged.
Atoms tend to be fixed in place.
Since the electron charge is negative, the current in a wire actually has a direction opposite the direction of motion of the electrons, as noted above. Fixed positive charge and negative charge moving to the right with speed in blown up segment of wire. If a conductor is in the form of a wire, we can compute the magnetic force on the wire if we know the number of mobile particles per unit length of wire , the charge on each particle , and the speed with which they are moving down the wire. The total force on a length of wire is , where is a unit vector pointing in the direction of motion of the particles through the wire. The quantity is called the current in the wire.