Electric Charges

    Study notes for the topic Electric Charges for your comparative exams. Basic Concepts, Types of charge, Conductors and Insulators, Methods of Charging, Conservation of Charge, Coulomb's Law, and mock test are below.

Basic Concepts

• The matter is made of atoms. Atoms have a positively charged nucleus (protons) and negatively charged electrons.
• Like charges repel, opposite charges attract.
• A charge is measured in Coulombs (C). The fundamental unit of charge is the charge on an electron (-1.6 x 10⁻¹⁹ C) or a proton (+1.6 x 10⁻¹⁹ C).

Types of Charge

• Positive charge: An object with a deficit of electrons.
• Negative charge: An object with an excess of electrons.

Conductors and Insulators

• Conductors: Materials that allow the easy flow of electrons (e.g., metals like copper, and silver).
• Insulators: Materials that resist the flow of electrons (e.g., rubber, plastic, glass).

Methods of Charging

• Friction: Transfer of electrons through rubbing materials together.
• Contact: Charge transfer through direct contact between a charged and uncharged object.
• Induction: Redistribution of charges within an object caused by the proximity of a charged object.

Conservation of Charge

The total charge in an isolated system remains constant. The charge can be transferred, but not created or destroyed.

Coulomb's Law

The force between two charges is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them.

Formula: F = k * (q1 * q2) / r²

• F = force (Newtons)
• k = Coulomb's constant (9 x 10⁹ N m² / C²)
• q1, q2 = charges (Coulombs)
• r = distance between charges (meters)