Chapter 18: Electric Field & Forces

electric charge

property of matter that causes it to experience a force in the presence of another electrically charged object

positive charge

opposite signs attract

negative charge

same signs repel

quantization

all magnitudes of net charge are integer multiples of e

ions

atoms/molecules whose net electric charge does not equal zero

cation

positive ion with less electrons (2)

anion

negative ion with more electrons (4)

law of conservation of electric charge

the net electric charge of an isolated system remains constant

conductors

charge can easily move through materials (metals)

insulators

charge cannot easily move through materials (non-metals)

coulomb’s law

determines the magnitude of the electric force between two charged objects

equation: F= k |q₁q₂| / r²

law of superposition

if more than one force is acting on an object, the net force acting on the object is found by adding the individual forces

polarization

when the charges within insulating atoms/molecules shift their arrangement in the presence of external charges

electric field (E)

a value at a location in space that tells us the electric force that will act on a 1 C charge placed at that location

• is a vector

• is produced by charges

• exists at all points surrounding a charge

• exerts electric forces on other charges

equation: E = F / q₀

electric field lines

point away from positive charges and point toward negative charges

parallel plate capacitors

consists of two conducting plates with equal and opposite charges

equation: E = q / ε₀A = σ / ε₀

electric flux (Φ_E)

the flow of the electric field through a given area

equation: Φ_E = E(upside down T)A = |E||A| cosΦ

gauss’s law

states that the net electric flux through a closed surface is proportional to the total charge enclosed within that surface

• for a closed surface with enclosed charge, a larger surface area is pierced by a weaker field

equation: Φ_E = q_enclosed / ε₀