In Depth Notes on Fundamental Physics II - Chapter 1: Electricity and Coulomb's Law

General Course Structure

  • Course: Fundamental Physics II Electricity (Chapter 1)
  • Instructor: Dr. Hoàng Thị Hồng Cẩm
  • Contact: hoang-thi-hong.cam@usth.edu.vn
  • Hours Overview:
    • Lectures: 2.0 hours per topic
    • Exercises: 1.0 hour per topic
  • Topics Covered:
    1. Coulomb's Law
    2. Electric Field
    3. Gauss' Law
    4. Electric Potential
    5. Magnetic Force and Magnetic Field
    6. Biot-Savart’s Law and Ampere’s Law
    7. Induction
    8. Motion of Charge in Electric and Magnetic Fields
  • Assessment:
    • Attendance/Attitude: 10%
    • Mid-term Test: 30%
    • Final Exam: 60%

1.0 Coulomb's Law Overview

1.1 Basic Principles

  • Early experiments showed that objects can become charged through friction (e.g., amber and straw).
  • Key Discoveries:
    • 1820: Connection between electricity and magnetism identified (Oersted's experiment).
    • 1873: Maxwell's equations unified the concepts of electricity and magnetism.

1.2 Electric Charge

  • Types of Charge:
    • Positive Charge: Attracts negative charges, repels positive charges.
    • Negative Charge: Attracts positive charges, repels negative charges.
    • Net Charge: In most objects, the total charge is zero (neutral).
  • Charge Behavior:
    • Rubbing rods generates charge, leading to either attraction or repulsion based on charge type.

1.3 Conductors and Insulators

1.3.1 Types of Materials

  • Conductors: Allow charges to move freely (e.g., metals, water).
  • Insulators: Do not allow free movement of charges (e.g., rubber, glass).
  • Semiconductors: Exhibit properties intermediate between conductors and insulators (e.g., silicon).
  • Superconductors: Perfectly conduct electricity without resistance at very low temperatures.

1.3.2 Charge Transfer

  • Induced Charge: Charge separation occurs in a neutral object due to the electric field of a nearby charged object.
  • Discharge: Process of neutralizing or transferring excess charge.

1.4 Coulomb's Law

1.4.1 Fundamental Equation

  • Coulomb's Law describes the electrostatic force between two charged particles: F{12} = k \frac{q1 q_2}{r^2}
    • Where:
    • $F_{12}$: the force between charges.
    • $k$: electrostatic constant ($k = 8.99 \times 10^9 \text{N m}^2/ ext{C}^2$).
    • $q1, q2$: magnitudes of the charges.
    • $r$: distance between the charges.

1.4.2 Force Directions

  • Attraction and Repulsion:
    • Same charge types repel each other.
    • Opposite charge types attract each other.