A potential or pressure builds up at one end of the wire, due to an excess of negatively charged electrons. It is like water pressure building up in a hose. The pressure causes the electrons to move through the wire to the area of positive charge. This potential energy is called Voltage , and its unit of measurement is the Volt . The number of electrons is called current and its unit of measurement is the Ampere or Amp .
Electrical current is like the amount or volume of water flowing through the hose.
An Ohm is the unit of measurement of the electrical resistance. A conductor like a piece of metal has its atoms so arranged that electrons can readily pass around the atoms with little friction or resistance. In a nonconductor or poor conductor, the atoms are so arranged as to greatly resist or impede the travel of the electrons. This resistance is similar to the friction of the hose against the water moving through it. Resistance can cause heat and light Electrical resistance is essentially friction within the wire.