Question

Which of the following charge distributions can be accurately replaced by a single charge of magnitude Q at the origin ( 0,y 0,or the purposes of calculating the electric field at the location 0m, y- 0m, z2m). a) a small solid sphere of radius r0.5m and with a uniformly distributed charge of Q b) a large solid sphere of radius r-4m and with a uniformly distributed charge of Q c) a small spherical shell of inner radius r1 0.3m, outer radius 72-0.5m, and a uniformly distributed charge of Q d) a medium-sized spherical shell of inner radius r - 1.5m, outer radius r2-2.5m, and a uniformly distributed charge of Q e) a large spherical shell of radius r 3.0m, outer radius r 5.0m, and a uniformly distributed charge ofQ f) two thin spherical shells, the first shell having a radius of ri 0.7m and a uniformly distributed charge of Qi; the second shell having a radius of r2- 1.3m and a uniformly distributed charge of Q2, where Q Q1Q2 9)8 equal positive charges,each of magnitude arranged in a cube centered on the origin. Select the correct answer O of 3 attempts used O only (a) and (b): both of the solid spheres O all (a)-(g) O only (a), (c), and (f): the small sphere, the small shell, and the two thin shells O only (c)-(1): all of the spherical shells. O only (a)-(f) all of the uniformly distributed spheres and shells O only (a) and (c): the small sphere and the small shell CHECK ANSWER

Answer 1

Only a c f that is a small sphere , small shell , two thin shells will behave as if all charge Q us at center or origin because if we will make a gaussian surface that is a sphere of radius 2m centered at origin we can use gauss law to find electric field at specified point and

It is surface integral of elecric field over a closed gaissian surface is equal to 1/epsilon_0 times charge enclosed by that surface

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