A thin spherical shell made of plastic carries a uniformly distributed negative

Question

A thin spherical shell made of plastic carries a uniformly distributed negative charge -6e-10 coulombs (indicated as -Q1 in the diagram). Two large thin disks made of glass carry uniformly distributed positive and negative charges 1.5e-05 coulombs and -1.5e-05 coulombs (indicated as +Q2 and -Q2 in the figure). The radius R1 of the plastic spherical shell is 7 mm, and the radius R2 of the glass disks is 4 meters. The distance d from the center of the spherical shell to the positive disk is 19 mm.

(a) Find the potential difference V1 - V2. Point 1 is at the center of the plastic sphere, and point 2 is just outside the sphere.
volts
(b) Find the potential difference V2 - V3. Point 2 is just below the sphere, and point 3 is right beside the positive glass disk.
volts

Remember that the sign of the potential difference is important.

Explanation / Answer

A) V= -E*L
E= (Q/A) / = ( Q_glass ) * (1/ (R_glass^2 * pi * 8.85 *10^-12) = 1.5e-5 / (16*8.85**e-12) = 3.4e4 N/C

l = 7 mm

V= -E*L=-3.4e4*7e{-3}=238 V

b)V= -E* l = - E * (0.019+0.007) = 3.4e4*(.026) =884V
Thus

V2 - V3=238 V+884V=1122 V

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