Electrostatics Chapter 32 Electrostatics Electricity at rest Involves

Electrostatics Chapter 32

Electrostatics • Electricity at rest – Involves electric charges, forces between them and their behavior in materials • Electricity = flow of electrons

Electrical Forces & Charges • Charges can either be attracting or repelling – Caused by protons (positive charge) and electrons (negative charge) – Like charges repel; opposite charges attract

Conservation of Charge • Electrons are neither created nor destroyed but are simply transferred from one material to another • Charge is conserved

Coulomb’s Law • for charged particles or objects – small compared with the distance between them, – force between the charges varies directly as the product of the charges and inversely as the square of the distance between them.

• F = k q 1 q 2 d 2 F= force between charges q 1= quantity of charge of one particle q 2= quantity of charge of other particle d= distance between charged particles k= proportionality constant (9. 0 x 109 Nm 2/C 2)

• Unlike gravitational forces, electrical forces can attract or repel. – Electrical forces > gravitational forces

Conductors & Insulators • Conductors – Materials whose outer electrons are free to roam (loosely bound) • Metals • Insulators – Electrons are tightly bound and remain with the atom (do not conduct electricity) • Rubber, wood, plastic

Charging by Friction & Contact • Electrons can be transferred from one material to another by touching (charging by contact) • Electrons can be transferred by friction when one object rubs against another

Charging by Induction • If a charged object is brought near a conducting surface, electrons will move even if there is no physical contact.

Charge Polarization • Occur when a charged object is brought near an insulator. – There is a rearrangement of the positions of charges within the atoms and molecules – One side is slightly positive, the other is slightly negative