electric flux and charge?

Question

the total flux from a cubical box 18cm on side is 1460 Nm/C. What charge is enclosed by the box?

Answer 1

use gauss theorem for enclosed charge

q = epsilon * phi
= 8.854*10^(-12) * 1460
= 1.29268E-08 Coulomb

Answer 2

you should establish an essential yet there's a extra intuitive physique of concepts. evaluate a cylinder enclosing the effective fee, the place the bases of the cylinder are on the y-z airplane and a airplane parallel to that, such that the fee is midway between the planes. the quantity of this flux is given only via Gauss' regulation. Now evaluate the decrease because of the fact the radius of this cylinder procedures infinity. The flux contained in the direction of the area is going to 0, as further and further of the linear container strains (evaluate the contribution only of the unmarried fee) get away out the bases. as a result interior the decrease, each and all of the flux is going contained in the direction of the bases and none contained in the direction of the area. via symmetry, you be attentive to that 0.5 the flux is going by using each and each base. as a result 0.5 the Gauss' regulation flux is going contained in the direction of the y-z airplane. The contribution of the damaging fee is precisely the comparable in value and direction. So the finished flux is two times 0.5 the Gauss' regulation flux contribution of only between the fees. So the finished flux is the comparable because of the fact the Gauss' regulation flux by using a closed floor containing 33.0 nC of fee.