Atomic Structure and Electron Theory

Atomic Structure of Matter

• Atoms are made up of a nucleus in the center, with electrons spinning around it in shells.
• The hydrogen atom, the simplest atom, has only one proton in its nucleus.
• The nucleus is always positively charged.
• The number of electrons spinning around the nucleus is always equal to the number of protons within the nucleus.
• Electrons in outer orbits are attracted to the nucleus by less force than electrons near the nucleus.
• Outer electrons can be easily forced from their orbits.
• In some materials, outer electrons leave their orbits and wander among the atoms at random, becoming free electrons.
• Outermost electrons are called valence electrons.
• The motion of free electrons creates an electric current.

Electron Theory

• When a positive charge is applied to an atom, it draws the outer electron away.
• This leaves the atom with more protons than electrons, making it positively charged, now called a positive ion.
• A positively charged ion attracts electrons from surrounding atoms and draws away their valence electrons.
• The flow of electrons toward a positively charged source is called “ELECTRON FLOW”.
• Electron movement takes place within the conductor at the speed of light as soon as the positive terminal attracts the valence electrons.
• Electron flow has visible and tangible effects like magnetic fields and heat.
• Electrons flow from negative to positive.
• The flow of electrons performs various tasks, including lighting, heating, powering electric motors, and enabling electronic applications.
• Imbalance in electrical potential creates an electron driving force, known as Electro-Motive Force or EMF.
• Electricity is generated by producing an EMF or an imbalance in potential.

Potential Difference

• One electron's potential difference is insignificant.
• It takes 6,250,000,000,000,000,000 electrons (six quintillion, two hundred and fifty quadrillion) to create a potential difference of 1 volt.
• When a switch is turned on, electrons flow from one potential difference to the other.
• The rate of electron flow is proportional to the potential difference.

Types of Electricity

• There are two basic types of electricity: current and static.
• 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 "wiped off" one and transferred onto the other.
• The material that loses electrons becomes electrically positive, while the material that gains electrons becomes electrically negative.
• Good conductors equalize charges as fast as they are created.
• Poor conductors have little equalizing current, allowing electrostatic charge to build up readily.
• Static charge is more readily created between non-conducting materials.
• Movement of fuel through a rubber transfer hose builds up potential differences due to relative movement.
• Aircraft movement through the air can build up huge potential charges on the aircraft skin.
• Aircraft earthing and electrical bonding are crucial to prevent sparking and safety hazards.

Voltage Produced by Pressure

• Compressing a quartz crystal creates charges on opposite surfaces.
• This phenomenon is called the piezoelectric effect.
• It can convert mechanical energy into electrical energy.
• It's not suitable for large voltage or power requirements.
• Microphones and barbecue lighters use this principle.

Voltage Produced by Heat

• When copper is heated, valence electrons move toward the cooler end.
• In iron, the opposite occurs, with electrons moving toward the hot end.
• Electrons flow through the hot junction.
• Electron flow is proportional to the intensity of heat.
• Electron flow (current) is measured to provide temperature indication.
• Thermocouples utilize this principle.

Voltage Produced by Light

• Light has energy, similar to any moving force.
• Some metallic substances are sensitive to light.
• When light strikes the surface of these substances, it dislodges valence electrons.
• Upon losing electrons, the photosensitive metal becomes positively charged.
• The EMF produced is called photoelectric voltage.
• Photo-cells use this principle, having a curved, light-sensitive surface focused on a central anode.
• Light striking the sensitive surface emits electrons toward the anode.
• Photo-cells have a very small power capacity.
• They are useful in detecting or controlling many operations accurately.

Voltage Produced by Chemical Action

• Two dissimilar metallic materials immersed in a solution can produce chemical action.
• One material has greater chemical action than the other, causing charged ions to form and producing an EMF.
• Wet cells have liquid electrolyte and must remain upright, commonly used in vehicle batteries.
• Dry cells have electrolyte mixed to form a paste, commonly found in torches and radio batteries.

Voltage Produced by Magnetism and Motion

• Three fundamental conditions must exist for voltage generation by magnetism:
  • A conductor where voltage will be produced.
  • A magnetic field in the conductor's vicinity.
  • Relative motion between the magnetic field and the conductor.
• The conductor must be moved to cut magnetic lines of force, or the magnetic field must be moved so that the flux cuts across the conductor.
• When the conductor cuts the lines of force, electrons are propelled in one direction, creating an electric force or voltage.
• Electromagnetic induction is the most common form of power generation, used in aircraft generators, alternators, and atomic, hydroelectric, and fossil fuel power plants.
• The amount of electricity produced depends on the rate at which lines of flux are cut.
• This rate can be increased by:
  • Increasing magnet strength.
  • Increasing conductor speed.
  • Increasing the number of conductors.

Summary

• Spinning a loop of wire in a magnetic field generates an EMF.
• The driving force doesn't matter, as long as there's relative motion between the conductor and the lines of magnetic flux.

Explore the fundamentals of atomic structure and the behavior of electrons in this quiz. Topics include the organization of atoms, the nucleus, and the concept of positive ions. Understand how free electrons contribute to electrical currents and the significance of valence electrons.