Section 1.1: Introduction to Charge

This section introduces electric charge as a fundamental property of matter, the types of charge, and basic observations in electrostatics.

Electric Charge:

Charge is a fundamental property of matter causing it to experience a force in the presence of other charges.

Types of charges: positive and negative.

Observation:

Like charges repel, opposite charges attract.

Charge is conserved and quantized: \( q = n e, \quad n \in \mathbb{Z} \)

Example 1

Two small spheres have charges \( q_1 = +2 \mu C \) and \( q_2 = -3 \mu C \). Describe the interaction.

The spheres have opposite charges, so they attract each other.

Identify the charge type for a proton and an electron.
Two charges \( +5 \mu C \) and \( +2 \mu C \) are placed 3 m apart. Predict the interaction.
Express a charge of \( 1.6 \times 10^{-19} \) C in terms of elementary charges.
If a neutral object gains electrons, what happens to its charge?
Explain why charge is considered quantized.