Conductors and Insulators
Electric conductors are substances or objects through which electric current moves easily. Electric nonconductors, or insulators as they are also called, are substances or objects through which electric current does not move easily.
As a general rule, metals are good conductors whereas nonmetals are poor conductors. Aluminum, copper, gold, iron, mercury, nickel, platinum, and silver are examples of good conductors. Some conductors are liquid or gas. Safety Tip: Water is a good conductor of electricity so don’t take your blow dryer or other electric powered device into the bathtub! Some nonconductors, such as rubber, plastic, and glass are used as insulators to protect against short circuits and electric shocks.
The difference between a conductor and an insulator is that in a conductor, there are free electrons, whereas in an insulator, all of the electrons are tightly bound to their respective atoms. In an uncharged body, there are an equal number of positive and negative charges. In metals, a few of the electrons are free to move from atom to atom.
Atoms want to be balanced, so the atom that has been "unbalanced" will look for a free electron to fill the place of the missing one. An unbalanced atom has a "positive charge" (+) because it has too many protons.
Since it got kicked off, the free electron moves around waiting for an unbalanced atom to give it a home. The free electron charge is negative, and has no proton to balance it out, so we say that it has a "negative charge" (-).
When electrons move among the atoms of matter, a current of electricity is created. This is what happens in a piece of wire. The electrons are passed from atom to atom, creating an electrical current.
Flash movie of an electric current in a metal conductor:
The following site has several great links to learn about Electricity. Try Brainpop and the Exploratorium.