5. 9/9 points ! Previous Answers MI3 167.P062. Two plastic spheres The figure sh

Question

5. 9/9 points ! Previous Answers MI3 167.P062. Two plastic spheres The figure shows two thin plastic spherical shells (shown in cross section) that are uniformly charged. The center of the larger sphere is at it has a radius of 12 cm and a uniform positive charge of 4 x 109 C. The center of the smaller sphere is at cm; it has a radius of 3 cm and a uniform negative charge of-1x 109 C My Notes (a) What is the electric field at location A (6 cm to the right of the center of the large sphere)? Neglect the small contribution of the polarized molecules in the plastic, because the shells are very thin and don't contain much matter. (b) What is the electric field at location B (15 cm above the center of the small sphere)? Again, neglect the small contribution of the polarized molecules in the plastic, because the shells are very thin and don't contain much matter. 363182N/C (c) What is the force on an electron placed at location B? -5.81e-17V ,2.913e-17 v' ,,/ >N

Explanation / Answer

Part a:

Electric Field at A

E due to positive charge = 0

r- = (25-6) = 19cm = 0.19m

E due to negative charge

E = kq/r2

E = 9x10-9*1 x 10-9/(0.19)2

E = 9/(0.19)2

E = 249.3 N/C

Part b:

Electric Field at Point B

El (electric field from large sphere) = kq1r2

here r = sqrt(0.252 + 0.152) = 0.2915

El = 9 x 109*4 x10-9 / (0.252 + 0.152))
El = 36 / 0.085
El = 423.53

x component = E1cos(theta)

x component = E1*(0.25/0.2915)

x component = 363.17 N/C

y component = E1sin(theta)

y component = E1*(0.15/0.2915)

y component = 217.74 N/C

E2 = 9 x 109*(-1) x10-9 / (0.152)
E2 = -9 / 0.0225
E2 = -400 N/C (only y component)

total y component = -400 + 217.74 = -182.25 N/C

<363.17 , -182.25, 0>

Part c:

Force on the electron at B is given by:
Fx = qe * Ex

Fx = -1.602 x 10-19 * 363.17
Fx = -5.81 x10-17 N

   
Fy = qe * Ey
Fy = -1.602 x 10-19 * -182.25
Fy = -1.602 x 10-19 * -182.25
Fy = 2.91 x 10-17 N

F <-5.81 x10-17 , 2.91 x 10-17 ,0>

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