Gauss's Law

Question 1

Gauss law relates ….

Answer 1

1. the electric field at point on a Gaussian surface to

2. the net charge enclosed by that surface

Question 2

Gauss consider ….

Answer 2

the charge distribution inside a hypothetical closed surface

Question 3

flux of air flowing is ….

Answer 3

the volume of air flowing through the surface per unit time

Φ = v · A

Question 4

flux of electric field passing through a Gaussian surface is ….

Answer 4

Φ = (lim △A to 0) ∑ E · A = f E · dA

the sum of the flux across the two disks

Question 5

Gauss’s Law

Answer 5

εο Φ = (q enc)

εο ∮ E · dA = (q enc)

Question 6

If (q enc) is positive ….

If (q enc) is negative ….

Answer 6

positive, net flux is outward of Gaussian surface

negative, net flux is inward of Gaussian surface

Question 7

from Gauss’a Law to Column’s Law

Answer 7

assume a spherical Gaussian Surface centered on a point charge  
εο ∮ E · dA = (q enc)
εο E ∮ dA = (q enc)
εο E ( 4πr² ) = (q enc)
E = q / ( εο 4πr² )

Question 8

導電體的表面電場

External Electric Field of a Charged Isolated Conductor

Answer 8

assume a cylindrical Gaussian surface is embedded in the section
εο E A = σ A
E = σ / εο
( σ is charge per unit area )

Question 9

E field induced by straight line charge

Answer 9

E = λ / 2π εο r
# λ = linear charge density 
# r = distance from line charge to test point

Question 10

E field induced by sheet of charge

Answer 10

assume a cylindrical Gaussian surface enclose a section of the sheet
εο ∮ E · dA = (q enc)
εο ( EA + EA ) = σ A
E = σ / 2 εο