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rsatchel
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Homework Statement
A thin spherical shell with radius R1 = 2.00 cm is concentric with a larger thin spherical shell with radius 6.00 cm . Both shells are made of insulating material. The smaller shell has charge q1=+6.00nC distributed uniformly over its surface, and the larger shell has charge q2=−9.00nC distributed uniformly over its surface. Take the electric potential to be zero at an infinite distance from both shells.
Part A: What is the electric potential due to the two shells at the following distance from their common center: r = 0?
Part B: What is the electric potential due to the two shells at the following distance from their common center: r = 3.00 cm ?
Part C: What is the electric potential due to the two shells at the following distance from their common center: r = 7.00 cm ?
Homework Equations
V = ∫E. dl = (k q) / r
Φ = q(enc) / ε0 = ∫E.dA
The Attempt at a Solution
I got Part A:
V for inner shell: V= (k q) / r = (8.99E9 * 6.00E-9) / 0.02 = 2700
V for outer shell: V = (k q) / r = (8.99E9 * -9.00E-9) / 0.06 = -1350
ΣV = 2700 + (-1350) = 1350V
I eventually got Part B:
V = -k q1 (1/0.03 - 1/0.02) = 899V
V = -k q2 (1/0.06 - 1/ 0.03) = -1350
ΣV = 899 - 1350 = -450V (Although the answer had to be changed to +450, not really sure why...Maybe V is magnitude)
I tried doing the same thing Idid for Part B for Part C and got stuck:
V = -k q1 (1/0.07 - 1/0.02) = 1930V
V = -k q2 (1/0.07 - 1/ 0.06) = -192V
ΣV = 1930 - 192 = 1740V, but that is apparently wrong...
I'm thoroughly confused :/