Gen Physics Q3 - L3: Electric Fields, Electric Flux, Gauss's Law

Electric Field

Exerts a force on other charged objects even if they are distanced from each other

Electric Field Space

Surrounds the charged body and displaces charged particles in it, causing electric force

Electric Field Lines

Used as a guide in mapping out direction of electric field forces

Michael Faraday

Pioneered the use of electric field lines of force

Positive Electric Field Charge

Field lines are directed outward

Negative Electric Field Charge

Field lines are directed inward

Origins of Electric Field Lines

Start from positively charged particles and end on negatively charged particles

Paths of Electric Field Lines

The lines neither intersect nor break as they pass from one charge to another

Strength of Electric Field Lines

Greater lines means a stronger electric field

Point Charge

Region of space around a source charge, when another object enters this field it experiences electric force

Electric Field due to Point Source Charge Formula

E = Fe/q0

where E = electric field
where Fe = electric force exerted on point charge
where q0 = electric charge

Electric Field Intensity

Strength of electric field at a point due to the source charge

Electric Field due to Point Charge Formula

E = k |q|/r²

where E = electric field
where k = Coulomb’s Constant
where q = Electric Charge
where r = Radius

Electric Flux

Number of field lines passing through a surface

Fluxus

Means to flow

Test Charge

Charge that experiences an electric charge after entering an electric field

Getting Electric Flux

Dot product of Electric field and area vector

Direction of Area Vector

Vector perpendicular to the area

Electric Flux Formula

θ = E . A

E . A = EA cos Θ

θ = Flux
E = Field
A = Area
Θ = Angle

(only use cos if there is an angle)

Cross Section Electric Flux

E (field) is perpendicular to A (area), and the angle between E and the line perpendicular to the surface is zero (Flux = EA) (theta = 0)

Titled Section Electric Flux

A (area) is tilted at an angle theta from the perpendicular line to E (field) (Flux = EA cos theta)

Vertical Section Electric Flux

A (area) is parallel to E (field) which is tilted at 90 degrees from the line perpendicular to E (Flux = EA cos 90 = 0)

Gauss’s Law

Total electric flux through a surface is total electric charge (qtotal) inside the surface divided by 𝝐0

Carl Friedrich Gauss

Related electric field, flux and charge together as one

Permittivity of free space constant (𝝐0)

8.8542 × 10^-12 c² / N . m²

Total Electric Flux

Φ𝒕𝒐𝒕𝒂𝒍 = 𝑬𝑨 𝒄𝒐𝒔 theta

or

Φ𝒕𝒐𝒕𝒂𝒍 = 𝒒𝒕𝒐𝒕𝒂𝒍 𝝐𝟎