01-Electric-Charge-and-Electric-Force

Lesson Overview

  • Topic: Electric Charge and Electric Force

  • Course: General Physics 2, Senior High School

Background on Electrostatics

  • Electrostatics: Study of interactions between electric charges at rest.

Electric Charges

  • Definition: Objects contain electric charges due to surplus or deficit of electrons.

  • Origin of Term: "Electric" derives from Greek word ‘elektron’ (amber).

  • Forming Charges: Elements can share or accept free electrons, leading to net positive or net negative charge.

  • Types of Electric Charges: Positive and negative charges exist, with interactions described by the Law of Electrostatics.

Static Electricity

  • Occurs when an object obtains a net electric charge, creating an imbalance.

Law of Conservation of Charge

  • States that the total electric charge in a closed system remains constant; charge cannot be created or destroyed, only transferred.

Conductors and Insulators

  • Conductors: Materials that allow electric charge to move easily.

  • Insulators: Materials that do not permit movement of electric charges.

  • Semiconductors: Materials that can act as either conductors or insulators depending on conditions.

Electrostatic Charging

  • Process: Movement of charges from one object to another leads to imbalance.

Types of Charging

  1. Conduction: Charging through physical contact; charges equalize between touching conductors.

  2. Polarization: Movement of charges within a conductor when near a charged object, without touching.

  3. Induction: Redirecting charges within a polarized conductor to establish a non-zero net charge.

Coulomb's Law

  • Describes the electric force between two point charges:

    • Formula: F = k * (|q1 * q2|) / r^2

    • Where k = Coulomb's constant; q1 and q2 are the charges; r = distance between charges.

Examples

  • Example 1: Charge transfer between two touching spheres.

  • Example 2: Electric force between a proton and an electron at the Böhr radius.

  • Example 3: Comparing electric repulsion with gravitational attraction for helium nucleus particles.

  • Example 4: Net force calculation on a -2 C charge in an array of charges.

References

  • Franklin, K., Yates, P., Wilcocks, L., Scott, T., Muir, P. (2011). Introduction to Biological Physics for the Health and Life Sciences. Wiley.

  • Young, H. D., Freedman, R. A., Ford, L. A., Sears, F. W. (2020). University Physics with Modern Physics (15th ed.). Pearson.