Question on Gauss law & charged disks

  • Thread starter mazen_zone
  • Start date
  • #1
17
0
hey everyone...

i want to know why can't we use Gauss law to calculate the electric flux density of a charged disk?

and how to calculate it "everywhere"? as coulomb's law calculates it at a certain point only...
 

Answers and Replies

  • #2
ZapperZ
Staff Emeritus
Science Advisor
Education Advisor
Insights Author
35,847
4,664
hey everyone...

i want to know why can't we use Gauss law to calculate the electric flux density of a charged disk?
You need to realize when Gauss's Law are typically used - in highly-symmetric situation where you can construct a Gaussian surface that will have an electric flux that is either a constant, or zero. When you can do that, then using Gauss's Law will be quite easy. If not, it is seldom solvable in closed form mathematically.

and how to calculate it "everywhere"? as coulomb's law calculates it at a certain point only...
That's not right. You CAN use Coulomb's law to calculate the field at any point - it doesn't mean you can solve it EASILY. Again, because of the lack of symmetry, calculating at field points off the axis of symmetry will make the solution more involved (you will end up with an infinite series since there may be no closed form of the solution). When you get to a graduate level E&M course using texts such as Jackson, you WILL learn how to solve this using "Coulomb's Law", i.e. using Green's function technique to solve the Poisson's equation.

Zz.
 
  • #3
17
0
yeah i know coulombs law can calculate the electric flux at any point, i meant i can't use it to derive a general formula to calculate the electric flux density at any point near the disk like Gauss law, but i have to remake the calculations at every point that i want the flux at...

correct me if I'm wrong...
 
  • #4
ZapperZ
Staff Emeritus
Science Advisor
Education Advisor
Insights Author
35,847
4,664
yeah i know coulombs law can calculate the electric flux at any point, i meant i can't use it to derive a general formula to calculate the electric flux density at any point near the disk like Gauss law, but i have to remake the calculations at every point that i want the flux at...

correct me if I'm wrong...
I have no idea what you just said.

Coulomb's Law IS a "general formula" to calculate E-field.

Zz.
 

Related Threads on Question on Gauss law & charged disks

  • Last Post
Replies
1
Views
692
Replies
8
Views
13K
Replies
1
Views
565
  • Last Post
Replies
5
Views
4K
  • Last Post
Replies
2
Views
2K
Replies
5
Views
13K
  • Last Post
Replies
4
Views
9K
  • Last Post
Replies
6
Views
2K
  • Last Post
Replies
4
Views
5K
  • Last Post
Replies
2
Views
1K
Top