- #1
Jimbob999
- 26
- 2
A disk with a uniform positive surface charge density lies in the x-y plane, centered on the origin. The disk contains 2.5 x 10-6 C/m2 of charge, and is 7.5 cm in radius. What is the electric field at z = 15 cm?
I have used the formula:
http://edugen.wileyplus.com/edugen/courses/crs7165/halliday9781118230725/c22/math/math121.gif
(if this picture doesn't appear it is E=o/2e0 x (1-(z/sqrt(z^2+r^2)))
Using 2.5x10-6C/M2 as my surface charge density, I get a final result of 1.5x10^4 N/C
However it isn't one of the answer options, although it is exactly half of one of the options, so I'd lean towards that if I was guessing.
Here are the possible options:
30 N/C
300 N/C
3000 N/C
3.0 x 10^4 N/C
3.0 x 10^7 N/C
I have used the formula:
http://edugen.wileyplus.com/edugen/courses/crs7165/halliday9781118230725/c22/math/math121.gif
(if this picture doesn't appear it is E=o/2e0 x (1-(z/sqrt(z^2+r^2)))
Using 2.5x10-6C/M2 as my surface charge density, I get a final result of 1.5x10^4 N/C
However it isn't one of the answer options, although it is exactly half of one of the options, so I'd lean towards that if I was guessing.
Here are the possible options:
30 N/C
300 N/C
3000 N/C
3.0 x 10^4 N/C
3.0 x 10^7 N/C