Electrostatics Cheat Sheet

Key Definitions

• Electric Charge: A property of matter that causes it to experience a force when placed in an electromagnetic field. ✅

• Coulomb's Law: The force between two point charges is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance between them. ✅

• Electric Field (E): A region around a charged particle where a force would be exerted on other charges. ✅

• Potential Difference (V): The work done per unit charge in moving a charge between two points in an electric field. ✅

Important Concepts

Electric Forces

• The force between two charges can be attractive or repulsive depending on their signs.

• Superposition principle applies: net force is the vector sum of individual forces.

Electric Field

• Direction is defined as the direction a positive test charge would move.

• Calculated using E = F/q, where F is the force and q is the charge. ✅

Capacitance

• Capacitance (C): Ability of a system to store charge per unit voltage, given by C = Q/V. ✅

• Common capacitor types: parallel plate, cylindrical, spherical.

Key Formulas

• Coulomb's Law:

• F: force between charges

• k: Coulomb's constant (8.99 × 10⁹ N m²/C²) ✅

• q1, q2: magnitudes of charges

• r: distance between charges

• Electric Field:

• E: electric field

• F: force on charge

• q: test charge

• Capacitance:

• C: capacitance

• Q: charge stored

• V: potential difference

Common Mistakes to Avoid

Common Mistake: Confusing electric field strength with electric potential. Remember, E is force per unit charge, while V is energy per unit charge.

Memory Tricks

Tip: "ELECTRIC" —

• Electric Field

• Law of Coulomb

• Energy stored in capacitors

• Capacitance

• Test charge

• Repulsion/Attraction

• Induction

• Conductors vs Insulators

Key Diagrams

Electric Field Lines:
  +q -----> E
  -q <----- E
Capacitor:
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