Electricity at the Atomic Level February 6, 2012

Objectives Define matter What is an atom? What are it’s components? How are different elements distinguished from each other? What are electrons, protons and neutrons. What kind of charges to they each have? Describe negative and positive ions Describe ionization What are the symbols for current, volatage and resistance?

Electricity at the Atomic Level

The Components of an Atom

The Two Laws of Electrostatic Charges Like Charges Repel Unlike Charges Attract + + + + - Proton Electron

Atomic Number The Number of Protons inside the nucleus of the atom determine the atomic number of the atom which is used to distinguish one element from another.

Shells & The Valence Shell Electrons orbit the nucleus of the atom. Each orbit is known as a shell. The Valance shell is the outer most shell on any Atom. The further away the valance shell is from the nucleus means it is easier for the atom to loose an electron.

Conductors/Insulators/Semiconductors A conductor is a material which contains many free electrons. These are good materials for carrying an electric current. An Insulator is a material which prevents the flow of electricity. A Semiconductor is a material that is in the middle. It can be altered to become either an insulator or a conductor

Ionization Atom - # protons = # electrons = Balanced Atom - # protons < # electrons = negative Ion Atom - # protons > # electrons = Positive Ion The Process of gaining and loosing electrons is called ionization. This is a key part of current flow.

Current is represented by the symbol I With some applied force, electrons will move from a negatively charged atom to a positively charged atom. This flow of electrons between atoms is called current. Current is represented by the symbol I

Voltage is represented by the symbol E When there is an abundance electrons at one end of a conductor and a lack of electrons at the other end, current will flow through the conductor. This difference in “pressure” is referred to as voltage. Key Words/Terms: Difference of Potential Electromotive Force (EMF) Voltage is represented by the symbol E

Resistance This is the opposition to the flow of electrons (current). Every material offers some resistance. Conductors offer very low resistance. Insulators offer high resistance. Resistance is represented by the Symbol R Resistance is measured in Ohms Ω