In a conductor, electrons are bound very loosely and are free to move around. These so-called free electrons can move freely through the material and respond to nearby positive and negative charges. Conductors have low resistance and transfer electric current well. Metals are generally good conductors, the best of which are:
Semiconductors have a small number of free electrons available and pass a limited amount of electrical current. Semiconductors are extremely important in modern electronics because they can be used to control the amount of current in an electrical system. Semiconductors can be “doped” or mixed with different types of materials to change their conductive properties. Some semiconductor materials , shown in order below, include silicon, graphite, germanium, and gallium arsenide phosiphide seen as the little plates inside the clear plastic LED. Different forms of gallium arsenide phospide glow red, orange, or yellow when a current passes through them, making the substance widely used in older light-emitting diodes .
• Solar cells
• Diodes, like LEDs
• Microprocessor Chips which run your computer.