lecture 1: coulomb's law, charge quantization, & charge conservation

conductors

allow charges to move easily

insulators

do not allow charges to move

induced charge

phenomenon where a neutral object acquires a net charge due to the influence of a nearby charged object, without direct contact

• only conduction electrons with their negative charrges can move; positive charges are fixed

coulomb’s law

F = k * (q1*q2)/r²

where k = 8.9 × 10^9 N*m²/C²

principle of superposition

Fnet = F1 + F2

charge quantization

the electric charge of any object can only exist in discrete units, which are whole number multiples of the fundamental charge of an electron (approximately 1.6 x 10^-19 Coulombs)

charge conservation

net charge of interacting charged particles does not change

how is an object grounded?

• a pathway of conductors between an object & earth’s surface can be set up

• when the object is neutralized, we have discharged the object

shell theory 1

a charged particle outside a shell with charge uniformly distributed on its surface is attracted or repelled as if the shell’s charge were concentrated at its center

shell theory 2

a charged particle outside a shell with charge uniformly distributed on its surface has no net force acting on it due to the shell