Atomic Structure and Electron Theory

Atomic Structure of Matter

• Atoms consist of a nucleus with electrons orbiting around it
• Hydrogen is the simplest atom, with one proton in its nucleus
• The number of electrons orbiting the nucleus always equals the number of protons in the nucleus
• Electrons in outer orbits are attracted to the nucleus by less force than electrons closer to the nucleus
• Outer electrons can be easily forced from their orbits, becoming free electrons
• Free electrons create an electric current.

Electron Theory

• When a positive charge is applied to an atom, the outer electron is drawn away.
• The atom now has more protons than electrons and is positively charged.
• Positively charged atoms attract electrons from surrounding atoms.
• The flow of electrons toward a positively charged source is called "electron flow."
• In a conductor connected to a source of electrons, the positive terminal attracts an electron.
• Electron movement happens within the conductor at the speed of light.
• An electron entering a conductor instantly forces another electron out from the other end.
• The flow of electrons performs work, such as powering lights, heating devices, electric motors, and electronics.
• An imbalance in electrical potential creates an electro-motive force (EMF), which is a driving force for electron flow.

Potential Difference

• One electron's potential difference is not practically useful.
• 6,250,000,000,000,000,000 electrons equal 1 volt.
• When a switch is turned on, electrons flow from one potential difference to another.
• The rate of electron flow is proportional to the potential difference.

Types of electricity

• Two main types of electricity are current and static electricity.
• Current electricity involves electrons moving through a circuit and performing work.
• Static electricity is more of a nuisance.

Voltage Produced by Friction

• When two materials are rubbed together, electrons are transferred from one material to the other.
• The material losing electrons becomes electrically positive, while the material gaining electrons becomes electrically negative.
• Good conductors equalize charges quickly, while poor conductors allow electrostatic charge to build up.
• Static charges are more readily created between non-conducting materials.

Voltage Produced by Pressure

• Compressing a quartz crystal creates charges on opposite surfaces.
• This phenomenon is known as the piezoelectric effect.
• The piezoelectric effect can convert mechanical energy into electrical energy.
• Microwaves and barbecue lighters utilize this principle.

Voltage Produced by Heat

• When copper is heated, valence electrons move towards the cooler end.
• In iron, electrons move towards the hotter end.
• Electron flow through the hot junction is proportionate to the intensity of heat.
• Thermocouples measure electron flow to indicate temperature.

Voltage Produced by Light

• Light has energy, similar to any moving force.
• Some metallic substances are sensitive to light.
• Light striking these surfaces dislodges valence electrons, creating a positive charge on the metal.
• The resulting EMF is known as photoelectric voltage.

Voltage Produced by Chemical Action

• Two dissimilar metallic materials immersed in a solution create a chemical reaction.
• One material has a greater chemical action, leading to the formation of charged ions and the production of EMF.
• Wet cells contain liquid electrolytes and must be kept upright.
• Dry cells have electrolytes mixed into a paste.

Voltage Produced by Magnetism and Motion

• To generate voltage through magnetism, three conditions must exist:
  • A conductor where voltage will be produced
  • A magnetic field near the conductor
  • Relative motion between the field and conductor
• The conductor must move to cut through magnetic lines of force, or the magnetic field must move across the conductor.
• This motion forces electrons in a specific direction, creating electric force or voltage.
• Electromagnetic induction is the most common form of power generation.
• Aircraft generators and alternators, as well as atomic, hydro-electric, and fossil fuel power plants, utilize this principle.

Voltage Produced by Magnetism - Summary

• Spinning a loop of wire in a magnetic field creates EMF.
• Relative motion between the conductor and magnetic flux lines is essential.

Generation of Electricity

• Light, heat, friction, pressure, chemical action, and magnetism and motion are all methods to produce electricity.

Production of Electricity by Different Methods

• Friction: Rubbing materials together
• Pressure: Using the piezoelectric effect of materials (quartz)
• Heat: Heating materials with different responses to temperature changes
• Light: Using the photoelectric effect where light dislodges electrons from metals
• Chemical Action: Creating chemical reactions between dissimilar metals
• Magnetism and Motion: Using relative motion between a conductor and a magnetic field.