Chapter 15 — Chapter 15 — Electrostatics

Charge: property of matter; two kinds — positive and negative; like charges repel, unlike attract; SI unit coulomb (C). Rubbing transfers electrons: material with greater electron affinity (position in triboelectric series) gains electrons (negative), other loses (positive) — e.g., glass rod with silk becomes +, polythene with wool −. Electrostatic induction: charging a body without contact by bringing a charged body near — charges separate; earthing then removing gives opposite charge. Charged comb attracts paper by induction; paper later falls when charge is shared/neutralized via contact/humidity. Gold-leaf electroscope: brass rod with disc and gold leaves in a glass case; leaves diverge when charged; detects charge, its nature (bring known charge: more divergence = same sign) and relative magnitude (degree of divergence).