#AP Physics C: E&M - Charge and Electrostatics Study Guide

Hey there! Let's get you prepped for the AP Physics C: E&M exam with a focused review of charge and electrostatics. We'll break down the key concepts, connect them to real-world examples, and make sure you're feeling confident. Let's dive in!

#1. Electric Charge Fundamentals

#1.1. What is Electric Charge?

• Electric charge is a fundamental property of matter that governs electromagnetic interactions.
• It's what makes things attract or repel each other electrically.
• Think of it as the 'stuff' that creates electric forces.

#1.2. Types of Charge

• There are two types of electric charge: positive and negative.
• Like charges repel each other (positive-positive or negative-negative).
• Opposite charges attract each other (positive-negative).

#1.3. Quantization of Charge

• Charge is quantized, meaning it comes in discrete units.
• The smallest unit of charge is the charge of a single electron or proton, denoted as e, where $e = 1.602 \times 10^{-19}$ Coulombs (C).
• Any observable charge is an integer multiple of e.

#2. Redistribution of Charge

#2.1. Methods of Charging

• Friction: Rubbing two neutral objects together can transfer electrons from one to the other. One object becomes positively charged, and the other becomes negatively charged. Example: Rubbing a balloon on hair.

• Contact: When a charged object touches a neutral object, charge can be transferred between them. This is also called conduction. The objects will end up with the same type of charge.

• Polarization: A charged object can induce a charge separation in a neutral object without direct contact. This happens when the charged object's electric field causes the charges within the neutral object to shift. Example: A charged rod attracting a neutral piece of paper.

#2.2. Charge Distribution Changes

• The distribution of charge in a system can change due to:

  • The presence of other charged systems.
  • Changes in the charge distribution of nearby systems.
  • Friction or contact between systems.
  • Polarization of one or both systems.

• Example: A positively charged rod br...