Electricity and magnetism with notes

Atomic Structure

  • Components of an Atom

    • Protons: Positively charged

    • Neutrons: No charge

    • Electrons: Negatively charged

    • The outer electron shell is called the valence shell.

  • Atomic Neutrality

    • Atoms are neutral when the number of protons equals electrons.

    • An atom can become charged with a surplus/deficiency of electrons, leading to electric charge.

  • Electron Configuration

    • Electrons orbit the nucleus in permitted shells or energy levels.

Electricity

Definition of Electrical Current

  • Electrical Current

    • Flow of charged particles in one direction.

    • In solids, it's typically free electrons in metals serving as conductors.

  • Good Conductors: Metals (silver, copper, aluminum, gold)

  • Poor Conductors: Plastics and rubber as insulators.

  • Current Measurement: Measured in Amperes (A).

Conductors, Insulators, and Semi-Conductors

  • Conductors: Allow easy flow of electrons (e.g., metals, water).

  • Insulators: Resist the flow of electrons (e.g., wood, plastic).

  • Semi-Conductors: Allow flow under specific conditions (e.g., silicon).

Conduction and Band Gaps

  • Conduction Band: Where electrons can move freely when excited.

  • Valence Band: Outermost orbital where electrons can occupy.

  • Band Gap: Energy difference between conduction and valence bands.

    • Large gap = insulator; small gap = conductor.

Static Electricity

  • Definition: Result of motionless charged bodies.

  • Charge Interactions: Like charges repel, unlike charges attract.

  • Force Dynamics: The force exerted is proportional to charge and inversely proportional to the square of the distance.

Quantifying Electricity

  • Current: Quantity of electrons (A).

  • Potential Difference: Difference between anode and cathode (V).

  • Power: Energy consumption rate (W).

Resistance and Conductivity

  • Resistance: Rate at which electrons are prevented from flowing (Ω).

    • Factors affecting resistance: length, cross-sectional area, and temperature of the conductor.

Electric Charge

  • Definition: Physical property of matter that experiences force in an electromagnetic field.

  • Types of Charge: Positive (protons) and Negative (electrons).

Electric Fields

  • Definition: Surround charged particles; responsible for attraction/repulsion.

  • Field Strength: Stronger near charged objects, decreases with distance.

Magnetism

Magnet Properties

  • Definition of a Magnet: An object that exerts a force on other magnetic materials.

  • Poles: North and South; like poles repel, unlike attract.

Domain Theory

  • Domains: Small regions in magnets that align in the same direction.

  • Types of Material:

    • Ferromagnetic: Strongly magnetic (e.g., iron).

    • Paramagnetic: Weaker magnetic properties (e.g., aluminum).

    • Diamagnetic: Non-magnetic materials (e.g., copper).

Electromagnetism

  • Creation of Magnetic Fields: Generated by current flowing through wire.

  • Solenoids and Electromagnets: Coils of wire that produce stronger magnetic fields when a core is added.

  • Applications in Radiography: Motors and generators using magnetic fields.

Transformers in Radiography

  • Function: Change AC voltages; step up or step down depending on requirements.

  • Efficiency: Not 100% efficient due to various losses (copper, iron).