TERMS:

• Test Charge: A mathematical construct-- a charge that does not exert any influence on surrounding particles but IS influenced by other electric fields.
• conductor - materials where electrons can roam
• insulator - materials that keep their electrons close to home
• coulomb - a unit of electrical charge (see below)

CONSTANTS:

• e^-_mass = 9.1 x 10^-31 kg
• charge of an electron = 1.60 x 10^-19 coulombs (C)
• k_e = 8.987 x 10⁹ Nm²/C²
• k_e = 1/4πε_o

FORMULISTICS:

Electrical Force: F_e = (k_eq₁q₂)/r²

Electrical Field:

• E = F_e / q_o where q_o  = a positive test charge

• E= (k_eq)/r²

Gauss's Law (for an object enclosing 1 or more charged particles)

• Φ = ∮E ∙A dA or ∮EAcosθ dA where θ is the angle between the electrical field line vector and the area vector

• Φ = q_in/ε_o : the electric flux through an ENTIRE gaussian surface is equal to the algebraic sum of the charges INSIDE the surface divided by the permitivity of free space

Generally: the more symetric the surface area of the gaussian surface the more accurate is this formula.

• What is the effect of presence or absence of charges inside a gaussian surface on any analysis of electric flux in and out of that surface?

• Why do we use the "dot" product of the area vector with the electric field vector when calculating electric flux?

• What is the effect of surface area symetry on any analysis of electric flux in and out of a gaussian surface?

• What is the effect of a uniform electric field on any anlysis of electric flux in and out of a gaussian surface?

• Mr Chase tells us (quite correctly by the by) that we can ALWAYS use:

Φ = q_in/ε_o

to calculate the electric flux through a gaussian surface. What are the limitations to this approach and when does it work best?